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Physics Physics Instrumentation and Detectors

physics.ins-det Watch Instrumentation and Detectors

Friday 28 August

Instrumentation and Detectors · Cross-listed from physics.app-ph

Extending the operating window of scanning electron microscopy through an integrated electron-optical architecture for high-temperature and near-ambient-pressure environments

Yue Chai, Honglong Zhao, Xinning Tian et al. (+2 more)

Scanning electron microscopy (SEM) under simultaneously high-temperature, near-ambient-pressure (NAP), and reactive-gas environments requires coordinated control of vacuum isolation, electron-beam transmission, signal generation, and thermal management, constraints that have long limited the operating window of environmental scanning electron microscopy (ESEM). Here we establish an integrated electron-optical architecture that combines a multistage differential-pressure pathway, front-stage pressure transition, detector optimization, thermal management, and a gas-focusing sampling architecture into a unified ESEM platform. Pressure distribution and electron-beam transmission are quantitatively validated through computational fluid dynamics (CFD), Monte Carlo electron-gas scattering analysis, and direct beam-current measurements, while detector optimization and thermionic-electron suppression preserve stable imaging under elevated pressure and temperature. The resulting system enables stable SEM imaging at pressures up to 20,000 Pa and high-temperature imaging up to 1,400 degrees C, continuous observation of hydrated biological specimens, and synchronized SEM-QMS operando characterization using local gas sampling. These developments establish a general electron-optical framework for extending ESEM toward realistic operando environments where elevated temperature, reactive gases, structural evolution, and gas-phase chemistry can be investigated simultaneously.
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All authors Yue Chai, Honglong Zhao, Xinning Tian, Chao Ang, Zhu-Jun Wang

Instrumentation and Detectors

Migration of Belle II TOP Feature Extraction from the Zynq Processing System to PCIe40 Readout PCs

Harsh Purwar, Shahab Kohani, Vasily Shebalin et al. (+11 more)

The Belle II Time-of-Propagation (TOP) detector is a key system for charged-particle identification (PID). Although TOP operated successfully during initial Belle II data taking, increasing luminosity and beam-induced background led to more frequent single-event upsets (SEUs) in the radiation-exposed Zynq systems-on-chip (SoCs). Resulting lockups of the embedded processing systems (PSs) interrupted data acquisition. To mitigate this limitation, waveform feature extraction, a critical task of the on-detector Zynq PS, was migrated to the off-detector PCIe40 readout PCs (ROPCs). The new architecture bypasses the PS in the event data path and performs feature extraction outside the detector radiation environment. This change removed SEU-induced PS lockups from the event data path and enabled stable operation of the TOP front-end electronics and the Belle II data-acquisition system under increased luminosity and background conditions. The typical TOP deadtime decreased from about 1% to a level consistent with zero after the final firmware patch, and stable operation was demonstrated at a Level-1 (L1) trigger rate of 30 kHz with a microchannel-plate photomultiplier-tube (MCP-PMT) hit rate of approximately 5 MHz per PMT. This paper describes the migrated architecture, its deployment and validation, and its operational and PID performance.
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All authors Harsh Purwar, Shahab Kohani, Vasily Shebalin, Martin Bessner, Matt Andrew, Thomas Browder, Tommy Lam, Kurtis Nishimura, Sourav Patra, Vladimir Savinov, Marko Staric, Gary Varner, Satoru Yamada, Keisuke Yoshihara

Thursday 27 August

Instrumentation and Detectors

The efficiency of moderating neutron detector: Monte Carlo simulation, experimental validation, and angular dependence

Carl R. Brune

This paper describes the Monte Carlo simulation and experimental validation of the neutron detection efficiency in a 4pi polyethylene moderating detector. The experimental validation was performed using several sources providing neutron energies from 10s of keV up to 14 MeV. The Monte Carlo simulations employed the MCNP6 code are believed to be accurate within 3% for neutron energies below 6 MeV. A new method for parametrizing the dependence of the efficiency on the neutron angular distribution for in-beam experiments is also presented. This approach utilizes a Legendre decomposition of the efficiency and allows all of the needed information to be extracted from a single simulation.
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Instrumentation and Detectors · Cross-listed from eess.SP

A Nonuniform-Sampling Theory for Static Multi-Threshold Sampling

Ao Qiu and Qingguo Xie

Multi-Threshold (MT) sampling fixes voltage levels and records when a waveform crosses them. The resulting signal-generated event stream is governed not by a prescribed clock but by the nonuniform geometry of the realized crossing set. Within classical nonuniform sampling, we develop a retained-event MT theory for static, uniformly spaced thresholds. For a realized retained MT time set, Beurling's weak-limit theorem gives the exact necessary-and-sufficient condition for stable sampling of $PW_\Omega$. For a fixed signal class, the same principle gives the a priori criterion: uniform stable MT sampling is equivalent to Bernstein uniqueness for every set in the class weak-limit hull. This criterion reduces to computable forms under structured priors. Periodic templates give finite fiber/rank tests, periodic-gap streams give a Shannon-type complete-interpolation boundary and a stable-sampling density rule, and finite-state gap priors reduce noncritical certification to a maximum-cycle-mean condition. Kadec-type local certificates, retained-density bounds, and finite-matrix tests provide practical sufficient conditions for finite active records, while conditional perturbation bounds quantify how jitter, front-end noise, and threshold error consume a clean sampling margin under event correspondence. The theory also identifies the unavoidable boundary of this model: unrestricted finite-energy retained MT records have zero full-line lower Beurling density and therefore cannot provide a universal prior-free sampling theorem for $PW_\Omega$. Within retained-event point sampling, the MT recovery question is resolved precisely: exact recovery is governed by event-set geometry, computable guarantees require structural priors or finite-dimensional/tail assumptions, and the unrestricted static finite-energy problem is impossible.
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Instrumentation and Detectors

Frequency Synchronization Circuit Model for Analog Vector-Matrix Multiplication in the Frequency Domain

Taeju Lee, Scott T. Habermehl, Timothy W. Caplice et al. (+3 more)

This work introduces a frequency synchronization circuit model for analog vector-matrix multiplication in the frequency domain. The frequency synchronization is implemented by coupling oscillators through all-to-all connections. Each oscillator is implemented using complementary cross-coupled transconductance pairs and RC high-pass filters. In this work, the frequency synchronization is achieved not only using oscillators alone but also through a configuration in which oscillators and resonator models (i.e., MEMS/NEMS resonators) are combined. While addressing the frequency synchronization of all the coupled oscillators, a partial synchronization is also discussed by controlling the coupling strength of a selected subset of oscillators. This frequency synchronization analysis focuses on the small-signal analysis using analog circuit and resonator models, thereby enabling an understanding of the synchronized frequency defined by the parameters of the analog circuit and resonator models.
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All authors Taeju Lee, Scott T. Habermehl, Timothy W. Caplice, Michael L. Roukes, Philip X.-L. Feng, Kenneth L. Shepard

Instrumentation and Detectors

A microwave SQUID multiplexing concept for macro-cryogenic calorimeter arrays

N. Ferreiro Iachellini, P. Szypryt, L. Canonica et al. (+10 more)

Massive cryogenic calorimeters read out by transition-edge sensors (TES) can reach eV-scale baseline resolution, but the single-channel dc-SQUID readout conventionally used in rare-event searches, with one amplifier chain and several wires per detector, limits practical arrays to a few tens of channels. We propose to apply microwave SQUID multiplexing ($\mu$MUX), developed for fast X-ray and neutrino-mass microcalorimeters, to massive BGO (Bi$_4$Ge$_3$O$_{12}$) calorimeters operated at $\simeq 20$~mK; sapphire and TeO$_2$ absorbers are covered by the same framework. Using the established thermal and noise model for massive TES calorimeters, we derive a noise model for the multiplexed readout, including the HEMT, two-level-system and SQUID contributions, and its scaling with the multiplexing factor $N_{\rm mux}$. Since the slow thermal signals require only about a kHz of sampling per channel, the limiting requirement is not bandwidth but an input-coil sensitivity of $( 0.1$ to $1)\,\mu$A$/\Phi_0$, a factor of $10$ to $30$ beyond current $\mu$MUX devices, matched to the detector current noise of ($9$ to $10$)~pA$/\sqrt{\rm Hz}$, which is independent of the absorber mass. With a total flux noise of $\simeq$$1.2\,\mu\Phi_0/\sqrt{\rm Hz}$, the readout degrades the baseline resolution by less than $2\%$ up to $N_{\rm mux}=1000$, negligible compared with the TES-limited resolution. These results are implemented in a single-tower design: 52 BGO crystals of 100~g each and one HEMT amplifier. The tower is the unit of a multi-tower array of several kilograms aimed at CE$\nu$NS and dark matter searches.
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All authors N. Ferreiro Iachellini, P. Szypryt, L. Canonica, W. B. Doriese, M. Durkin, A. Giachero, J. A. B. Mates, A. Nucciotti, L. Pattavina, S. Quitadamo, C. Shiu, J. N. Ullom, M. R. Vissers

Instrumentation and Detectors

Design and performance of the Fast Beam Condition Monitor for luminosity and background measurement at the CMS Experiment in LHC Run 3

The CMS BRIL Collaboration: Eliana Acurio, Ying An, Iakov Andreev et al. (+110 more)

The Fast Beam Condition Monitor (BCM1F) has been used at the CMS Experiment since the first LHC circulating beams in 2008. Originally meant as a beam-induced background monitor for fast beam losses detection, it showed a potential also for luminosity measurements in 2012 running, and has been used for luminosity measurements since the beginning of Run 2 data taking in 2015 as a part of the Beam Radiation, Instrumentation and Luminosity (BRIL) system. Over the years, the system has undergone various upgrades to the sensors, the front-end and back-end electronics, providing improvements in the precision of the measurements, that remain valid in the higher pileup conditions of LHC Run 3 (2022-2026). Based on the experience of all BCM1F Run 2 upgrades, the detector was completely rebuilt prior to LHC Run 3 using AC-coupled silicon-pad diodes and active cooling. This latest detector version exhibits excellent linearity with instantaneous luminosity and achieves nanosecond-level timing precision, enabling improved systematic corrections for luminosity and background measurements. This paper presents a detailed overview of the detector system for LHC Run 3, including the selection and qualification of sensors as well as a summary of the readout system. It also outlines the processing and calibration strategy for luminosity data, discussing operational hurdles and comparing BCM1F measurements to other CMS luminosity measurements to assess the system's performance as a luminometer. Lastly, the implications for the design of a future luminosity detector to be used in the envisioned HL-LHC upgrade are discussed.
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All authors The CMS BRIL Collaboration: Eliana Acurio, Ying An, Iakov Andreev, Tomas Atehortua, Georg Auzinger, Hamed Bakhshiansohi, Gergely Balint, Luis Ignacio Banos, Juan Pedro Barajas Ibarria, Hugo Alberto Becerril, Jose Feliciano Benitez, Philip H. Butler, Alan Campbell, Edgar Fernando Carrera Jarr{\i}n, Alfredo Castaneda Hernandez, Marco Costa, Antonio Cota Rodriguez, Luis Enrique Cuevas Picos, Anne Dabrowski, Vladyslav Danilov, Andres Guillermo Delannoy Sotomayor, Hedwin Aaron Encinas Acosta, Krisztian Farkas, Anna Feherkuti, Mahmoud Moussa Abdelkhalek Gadallah, Luis Gabriel Gallegos Marinez, Angela Giraldi, Alfredo Gurrola, Moritz Guthoff, Mykyta Haranko, Maria Hempel, Hans Henschel, Shilpi Jain, Armin Kadlecsik, Jan Kaplon, Adam Kardos, Olena Karacheban, Nimmitha Karunarathna, Joscha Ahauser, Georgios Krintiras, Leen Lambers, Jessica Leonard, Moises David Leon Coello, Maksim Jenihhin, Willard Johns, Markus Klute, Wolfgang Lange, Kuan-Yu Lin, Wei Heng Liu, Wolfgang Lohnmann, Arkady Lokhovitskiy, Robert Loos, Peter Major, Sophie Mallows, Jeremiah Mans, Daniel Marlow, Badder Marzocchi, John-Erik Meißner, Philip Jason Meltzer, Stefano Mersi, Andreas Bernhard Meyer, Dmitri Mihhailov, Valeria Monti, Michele Mormile, Javier Alberto Murillo Quijada, Vlodymyr Myronenko, Cristina Oropeza Barrera, Younes Otarid, Christopher Palmer, Jose David Ochoa Flores, Michelangelo Pari, Gabriella Pasztor, Marek Penno, Fabio Lucas Pereira Carneiro, Elena Popova, Attila Jozsef Radl, Evan Altair Ranken, Beatriz Ribeiro-Lopes, Francesco Romeo, Carlos Romero, Jonas Rubenach, Alexander Ruede, Vladimir Ryjov, Santeri Saariokari, Alessia Saggio, Valerie Scheurer, Vahid Sedighzadeh Dalavi, Mohammad Sedghi, Tatiana Selezneva, Konstantin Sharko, Alexey Shevelev, Konstantin Shibin, Sunil Somalwar, Rafael Sosa, Stefan Spanier, David Stickland, Robert Stone, Andromachi Tsirou, Oleksii Turkot, Lizardo Valencia Palomo, Cristina Vazquez Velez, Roger Rusack, Paola Tropea, Balazs Ujvari, Mayda Velasco, Piero Giorgio Verdini, David Walter, Joanna Wanczyk, Jesus Alberto Velazquez Corral, Daniel John Wilbern, Zhen Xie, Maryam Zeinali, Wolfram Zeuner

Instrumentation and Detectors · Cross-listed from physics.flu-dyn

High-resolution in situ analysis of biomass pyrolysis by combining quantitative synchrotron $\mu$CT and 3D particle-resolved simulations

Emeric Boigné, Mohamed M. Ahmed, Collin Foster et al. (+7 more)

Understanding the coupling between transport, chemical kinetics, and structural response within solid fuel combustion requires in situ measurements at high spatial resolution. To examine the dynamics of biomass pyrolysis, we optimize synchrotron X-ray micro-computed tomography ($\mu$CT), and conduct 3D particle-resolved simulations. A micro-focused heating cell with controlled heating and flow rate is employed, achieving temperatures of up to 1240 K and 3D imaging at 3.24 $\mu$m spatial and sub-minute temporal resolutions. The pyrolysis of three biomass materials at sample heating rates of 10-14 K/min are examined. The $\mu$CT measurements capture pore deformation, cracking, anisotropic shrinkage, and provide simultaneous thermogravimetric and thermovolumetric analyses to examine specific secondary pyrolysis pathways. Complementary 3D simulations considering detailed kinetics and structural response reproduce the key trends observed, and identify deficiencies in capturing simultaneous mass and volume losses during pyrolysis.
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All authors Emeric Boigné, Mohamed M. Ahmed, Collin Foster, Edna R. Toro, Dilworth Y. Parkinson, Alastair A. MacDowell, Harold S. Barnard, Francesco Panerai, Chiara Saggese, Matthias Ihme

Instrumentation and Detectors

AlGaN/GaN Hall-Effect Sensor for In-Situ Magnetic Field Monitoring of the HSX Stellarator

Yiming Zhao, Wayne Goodman, Thomas Gallenberger et al. (+3 more)

Direct magnetic field sensors can address integration drift commonly observed in conventional inductive magnetic diagnostics used in fusion systems. In this work, an AlGaN/GaN Hall-effect sensor was fabricated, packaged, and deployed inside the Helically Symmetric eXperiment (HSX)—the first quasi-helically symmetric stellarator, operating with a 1 T on-axis magnetic field and up to 200 kW of launched electron cyclotron resonance heating (ECRH) power—for in-situ magnetic field monitoring near the plasma edge. The sensor leverages the high-mobility two-dimensional electron gas (2DEG) formed in the AlGaN/GaN heterostructure for sensitive magnetic field measurement, while the wide-bandgap GaN material system provides thermal robustness for harsh-environment operation. During 68 consecutive plasma discharge shots, the sensor remained functional and produced clear transient responses associated with plasma ignition and discharge dynamics. Comparisons between biased and unbiased operation, as well as plasma-discharge and coil-only shots, confirmed that the response originated from the biased Hall-effect sensor element. Furthermore, the sensor output exhibited temporal correlation with the plasma stored energy measured by the HSX diamagnetic loop across high-energy, late-breakdown, and failed-breakdown discharges.
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All authors Yiming Zhao, Wayne Goodman, Thomas Gallenberger, Jasmine M. Cox, Benedikt Geiger, Debbie G. Senesky

Instrumentation and Detectors

Measuring and Modelling Lag in Amorphous Silicon Flat-Panel X-ray Detectors

Yiyue Huang, Benjamin Young, Andrew Kingston et al. (+1 more)

Detector lag, also referred to as afterglow, is a source of image degradation in flat-panel x-ray detectors, producing temporal artefacts that reduce image quality and quantitative accuracy. In this work, we present a robust and repeatable experimental framework for characterising long-term detector lag (from minutes to hours) under controlled step-up and step-down exposure transitions of particular relevance to tomography. The measured transition curves from an amorphous silicon detector with a CsI:Ti scintillator exhibit unexpected behaviour, with the detector response temporarily overshooting its final equilibrium intensity following step-up transitions, rather than exhibiting the gradual monotonic rise and decay typically expected. These curves were well fitted by multi-exponential functions, providing initial estimates for the depth of the charge traps in the scintillator. These parameters were incorporated into a proposed multi-trap rate equation model that reproduces the overall observed behaviour of both step-up and step-down transitions, including the overshoot that is not captured by previous models. Although discrepancies remain between the model and observation, this work establishes a reproducible methodology for detector lag characterisation and presents an improved physical model that offers greater insight into the mechanisms governing detector lag.
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All authors Yiyue Huang, Benjamin Young, Andrew Kingston, Adrian Sheppard

Wednesday 26 August

Instrumentation and Detectors · Cross-listed from physics.optics

HoloCMA: A Holographic Eye on Coarse-Mode Aerosols

Nikil Krishnakumar, Ryne A. Juidici, Nicholas Bravo-Frank et al. (+8 more)

Coarse-mode aerosols (CMAs), including pollen, spores, and dust, remain difficult to characterize in situ because conventional instruments rarely resolve particle geometry and number concentration together. We present HoloCMA, which combines digital inline holography, numerical reconstruction, and deep learning-assisted analysis for particle-resolved measurement. Its optical system targets particles from approximately 5.0 um to the millimeter scale. HoloCMA supports active sampling at up to 30.0 L/min and converts to open-path operation by removing the sampling module. With an NVIDIA GeForce RTX 5070 Laptop GPU and 8 GB VRAM, HoloCMA reports equivalent circular diameter (ECD) and number concentration in real time without sustained queue buildup up to 11.4 particles/cm3. Additional computing could extend real-time analysis to the workflow limit of 100.0 particles/cm3. We evaluated HoloCMA using polystyrene latex spheres, sodium chloride and ammonium sulfate crystals, and oleic acid droplets with nominal diameters of 4.9-11.8 um, with an Aerodynamic Particle Sizer (APS) for comparison. Across 12 comparisons, absolute differences between HoloCMA and corrected APS geometric-mean diameters ranged from less than 0.1 to 1.0 um, with a mean absolute difference of 0.5 um and a mean absolute relative difference of 8.4%. HoloCMA measures geometric size directly from reconstructed contours, whereas converting APS aerodynamic diameter requires material-specific assumptions. The APS-to-HoloCMA concentration ratio generally decreased with particle size, consistent with size-dependent transport and counting losses in the APS, although the cause could not be determined conclusively. HoloCMA thus enables continuous CMA measurements that combine geometric size, number concentration, and retained particle images, supporting classification and long-term atmospheric, environmental, and indoor-air monitoring.
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All authors Nikil Krishnakumar, Ryne A. Juidici, Nicholas Bravo-Frank, Shibo Wang, Qisheng Ou, Francisco J. Romayb, Wing Lai, Chongai Kuang, Naruki Hiranuma, David Y.H. Pui, Jiarong Hong

Instrumentation and Detectors · Cross-listed from physics.optics

Loss-tolerant hybrid metasurface mirror for reducing coating Brownian noise in precision optical cavities

Swadha Pandey, Evan D. Hall, Peter Fritschel et al. (+1 more)

We propose a hybrid mirror design that places an embedded metasurface beneath a Bragg reflector, combining the low coating Brownian noise of metasurface mirrors with the low optical loss of conventional multilayer coatings. Unlike previous hybrid designs, which place the metasurface at the input surface, our design positions it below the Bragg stack, reducing the optical field incident on the loss-prone resonant layer. For a design operating at 1064 nm, we show that this reduces absorption from 24 ppm for a bare metasurface to 7 ppm for the hybrid. We introduce a general method for calculating the coating Brownian noise of hybrid metasurface-multilayer mirrors at arbitrary coupling strength, extending prior methods to coherently combine a beam-scale mean-field contribution with the periodic, sub-wavelength-scale response of the metasurface. Applying this to our design, we find a reduction in Brownian noise amplitude spectral density relative to an equivalent-reflectance Bragg mirror by a factor of 1.6. Finally, we show that this design has higher angular tolerance than a bare metasurface mirror, maintaining higher reflectance over an angular range of 1 degree. This work provides a practical path towards incorporating low-noise metasurface mirrors into precision optical cavities, while minimizing optical loss and angular sensitivity.
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All authors Swadha Pandey, Evan D. Hall, Peter Fritschel, Matthew Evans

Instrumentation and Detectors · Cross-listed from astro-ph.CO

Paleo-Detectors as a Novel Probe of Dark Matter-Nucleus Effective Interactions

Dionysios P. Theodosopoulos

Paleo-detectors are a proposed approach to the direct detection of dark matter (DM) based on the observation of DM-induced nuclear recoils. Rather than relying on large detector masses required for conventional detectors, paleo-detectors exploit extremely long integration times, using small samples of naturally occurring minerals that have resided deep underground and accumulated damage tracks over geological timescales of order a gigayear. In this contribution, we review recent theoretical predictions for the sensitivity of paleo-detectors to WIMP-nucleus interactions within the framework of a Non-Relativistic Effective Field Theory (NREFT). We discuss both elastic and inelastic scattering processes and consider isoscalar couplings, taking into account backgrounds from neutrinos and radiogenic sources. We present projected sensitivities of paleo-detectors for different readout and exposure scenarios and compare the reach of paleo-detectors to that of conventional direct-detection experiments. For DM masses in the range $1\ \mathrm{GeV}/c^2$-$10\ \mathrm{GeV}/c^2$, paleo-detectors are expected to achieve sensitivities exceeding those of conventional experiments for WIMP-nucleus interactions mediated by all NREFT operators, with only a weak dependence on the read-out scenario or target mineral. For larger DM masses, $10\ \mathrm{GeV}/c^2$-$5\ \mathrm{TeV}/c^2$, paleo-detectors are projected to attain sensitivities comparable to or surpassing conventional experiments for interactions mediated by several NREFT operators, depending on the specific read-out scenario and choice of target mineral.
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Instrumentation and Detectors

Signal formation and induction-gap optimization in a THGEM coupled to a resistive plate anode

Arpan Maity, Luca Moleri, Maryna Borysova et al. (+1 more)

A Thick Gaseous Electron Multiplier (THGEM) detector coupled to a resistive plate anode was investigated for the first time, using an Ar:CO$_2$ (93:7) gas mixture. The resistive anode concept enabled stable operation with induction gaps significantly smaller than those typically employed in THGEM detectors, opening the possibility of improving signal formation and timing performance. The effect of the induction gap on the detector current- and charge-signal characteristics was systematically investigated. An optimal induction gap of 0.2 mm was identified based on several key signal parameters. Subsequently, detailed studies were carried out for this optimal configuration under different electric-field settings. The detector achieved a highest peak amplitude of $\sim$56 $\mu$A with a rise time of $\sim$5 ns at $\Delta\text{V}_{\text{THGEM}}$=1900 V, $\Delta\text{V}_{\text{induction}}$=100 V, and a drift field of 1 kV/cm when irradiated with 5.9 keV X-rays. Under the same operating conditions, a time resolution of $\sim$6.0 ns was measured detecting cosmic muons. This study establishes a new THGEM detector configuration and provides guidance for its potential application in particle-detection systems, such as muon spectrometers and sampling elements of digital hadronic calorimeters.
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All authors Arpan Maity, Luca Moleri, Maryna Borysova, Shikma Bressler

Instrumentation and Detectors

Development and Commissioning of the Cryogenic Target Detectors for the Technical Run of the NUCLEUS Experiment

N. Schermer, H. Abele, G. Angloher et al. (+57 more)

The NUCLEUS experiment aims to study coherent elastic neutrino-nucleus scattering (CE$\nu$NS) of reactor electron antineutrinos at the Chooz nuclear power plant in France. In this work, the cryogenic target-detector module for the NUCLEUS Technical Run was developed and commissioned at the Technical University of Munich. The module comprises four gram-scale CaWO$_4$ detectors, each equipped with two Transition Edge Sensors (TES), providing a total target mass of 6.96 g. We present the design, integration, detector characterization, and X-ray-based energy calibration of these detectors. Across six characterized detectors, a mean baseline resolution of $\overline{\sigma}_{\mathrm{BL}} = (2.79 \pm 0.60)\,\mathrm{eV}$ was achieved. The best-performing detector reached $\sigma_{\mathrm{BL}} = (2.16 \pm 0.02_{\mathrm{stat}})\,\mathrm{eV}$, surpassing the design goal by a factor of two and representing a state-of-the-art result for a cryogenic CaWO$_4$ detector. The target detector module was successfully operated simultaneously with the surrounding Cryogenic Outer Veto, which consists of six kg-scale Ge detectors for background discrimination, showing no measurable cross-talk. These results demonstrate the readiness of the target-detector system for the NUCLEUS Technical Run at Chooz and mark a key milestone in the development of cryogenic detectors for reactor-CE$\nu$NS measurements.
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All authors N. Schermer, H. Abele, G. Angloher, B. Arnold, M. Atzori Corona, A. Bento, E. Bossio, F. Buchsteiner, J. Burkhart, F. Cappella, M. Cappelli, N. Casali, R. Cerulli, A. Cruciani, G. Del Castello, S. Dorer, A. Erhart, M. Friedl, S. Fichtinger, V.M. Ghete, M. Giammei, J. Hakenmüller, D. Hauff, M. Hock, F. Jeanneau, E. Jericha, M. Kaznacheeva, H. Kluck, A. Langenkämper, T. Lasserre, D. Lhuillier, M. Mancuso, B. Mauri, A. Mazzolari, L. McCallin, H. Neyrial, C. Nones, L. Oberauer, L. Peters, F. Petricca, W. Potzel, F. Pröbst, F. Reindl, M. Romagnoni, J. Rothe, J. Schieck, S. Schönert, C. Schwertner, L. Scola, L. Stodolsky, A. Schröder, R. Strauss, R. Thalmeier, C. Tomei, L. Valla, M. Vignati, M. Vivier, A. Wallach, P. Wasser, L. Wienke

Tuesday 25 August

Instrumentation and Detectors · Cross-listed from astro-ph.IM

Engineering of titanium transition edge sensor wafers for the BA4-90/150 receiver of BICEP Array

A.Patel, P. A. R. Ade, Z. Ahmed et al. (+83 more)

BA4-90/150, the fourth receiver to be deployed in the BICEP Array (BA) series, is a dichroic 90/150 GHz instrument targeting the frequency space where sensitivity to the CMB polarization is maximized. The receiver will be deployed in the 2026-2027 austral summer, and is set to position BA to achieve exceptionally precise measurements of cosmic microwave background (CMB) polarization and strengthen constraints on inflationary models. Recent measurements in existing BA receivers suggest that unexpectedly high loop gain in the titanium (Ti) transition edge sensors (TESs) produces excess high-frequency noise that is consequently aliased down into the science band through the time-division multiplexed readout. To reduce the loop gain, we fabricated and tested prototype Ti TES wafers containing 16 modified detector architectures designed to broaden the superconducting transition and reduce the transition steepness (alpha). We present detector performance results, which will directly inform the final integrated wafer now being designed for full receiver commissioning.
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All authors A.Patel, P. A. R. Ade, Z. Ahmed, M. Amiri, D. Barkats, R. Basu Thakur, C. A. Bischoff, D. Beck, J. J. Bock, V. Buza, B. Cantrall, J. R. Cheshire IV, J. Connors, J. Cornelison, M. Crumrine, A. J. Cukierman, E. Denison, L. Duband, M. A. Echter, M. Eiben, B. D. Elwood, S. Fatigoni, J. P. Filippini, A. Fortes, M. Gao, C. Giannakopoulos, N. Goeckner-Wald, D. C. Goldfinger, S. Gratton, J. A. Grayson, A. Greathouse, P. K. Grimes, M. Halpern, S. Henderson, T. D. Hoang, J. Hubmayr, H. Hui, K. D. Irwin, M. Izquierdo Poza, J. H. Kang, K. S. Karkare, S. Kefeli, J. M. Kovac, C. Kuo, K. Lasko, K. Lau, M. Lautzenhiser, T. Liu, S. C. Mackey, N. Maher, K. G. Megerian, L. Minutolo, L. Moncelsi, Y. Nakato, H. T. Nguyen, R. O'Brient, S. N. Paine, M. A. Petroff, A. R. Polish, T. Prouve, C. Pryke, C. D. Reintsema, T. Romand, M. Salatino, A. Schillaci, B. Schmitt, B. Singari, A. Soliman, T. St. Germaine, A. Steiger, B. Steinbach, R. Sudiwala, K. L. Thompson, C. Tucker, A. D. Turner, C. Vergès, A. G. Vieregg, A. Wandui, A. C. Weber, J. Willmert, W. L. K. Wu, H. Yang, C. Yu, L. Zeng, C. Zhang, S. Zhang

Instrumentation and Detectors · Cross-listed from cs.AI

Agentic AI for operating scientific instruments for nanoscale characterization

Zahra Ayar, Marcos Penedo, Mahdi Mehdikhani et al. (+3 more)

Operating a scientific instrument such as an atomic force microscope (AFM) requires continuous expert decision-making. A trained user defines the experimental intent, translates it into instrument commands, assesses incoming data, adjusts imaging parameters, and post-processes the final image. Existing automation usually addresses only parts of this workflow through hard-coded routines, task-specific controllers, or trained machine-learning models. Here we present an agentic-AI framework that operates the executable part of the AFM workflow using a general-purpose, tool-augmented large language model connected to instrument functions through the Model Context Protocol (MCP). The framework consists of 3 MCP-based agents: AFM Messenger converts natural-language instructions into checked instrument commands; AFM Pilot assesses image quality through a large language model (LLM) and, if necessary, adapts imaging parameters; and AFM Doctor diagnoses image artifacts and applies transparent post-processing from a pre-approved tool set. Because the language model performs image assessment rather than a fixed scalar objective or external optimizer, the same strategy can be applied across sample types and imaging modes without specific retraining. Safe hardware operation is enforced through an ambiguity check layer before execution. Benchmarking against fine-tuned and off-the-shelf tool-using models shows that this guarded execution layer, rather than model capability alone, reduces wrong-command execution to zero. In live experiments on different samples, AFM Pilot matched expert operators in image quality, iteration count, and tuning time, with no significant difference. These results demonstrate a safe route to agentic operation of scientific instruments, where experimental intent remains human-defined while command execution, image-based tuning, and post-processing are delegated to AI agents.
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All authors Zahra Ayar, Marcos Penedo, Mahdi Mehdikhani, Nahid Hosseini, Prabhu Prasad Swain, Georg E. Fantner

Instrumentation and Detectors · Cross-listed from physics.acc-ph

High-charge collimated and energy-selected laser-driven MeV electron beams produced by magnetic selection

I. Cohen, I. Slabu, Q. Peysson et al. (+16 more)

We have developed a compact passive energy-selector for MeV-range electrons produced by irradiating solid targets by ultra-intense short-pulse lasers. The device allows for generating electron beams with a variable energy spread over a broad range of energies, from tens of keV to tens of MeV. Here we have demonstrated its use by producing electrons from solid targets in the MeV range and with a ~10% bandwidth, thereby compensating the intrinsic broadband nature of the electrons produced from such source. Coupled with a pulsed magnetic field to further compensate the intrinsic large divergence of this source, it allows to produce a highly-collimated beam of narrow-band and ultra-fast electrons, suitable for a wide range of applications, e.g. radiation therapy or time-resolved electron probing.
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All authors I. Cohen, I. Slabu, Q. Peysson, S. Dorard, Y. Abe, J. Béard, T. Moraine, S.N. Chen, A. Chessa, K.Iida, P. Kempski, Y. Kuramitsu, H. Kusano, F. Nikaido, M. Ruszkowski, K. Sakai, N. Tamaki, O. Tesileanu, J. Fuchs

Instrumentation and Detectors

Aliased noise characterization and mitigation in BICEP Array 150, 220 and 270 GHz time-division multiplexed detectors

S. Fatigoni, P. A. R. Ade, Z. Ahmed et al. (+83 more)

Early observations with the BICEP Array 150 GHz (BA2-150) and 220/270 GHz (BA3-220/270) receivers revealed detector noise equivalent temperatures (NETs) higher than expected, together with substantial detector-to-detector and module-to-module scatter. Noise measurements acquired with multiplexing off and high frequency sampling demonstrate that this excess originates from elevated high-frequency detector noise that aliases into the science band during time-division multiplexing. We show that the excess high-frequency noise is correlated with anomalously large logarithmic TES transition slopes, {\alpha}, resulting in elevated electrothermal loop gain and operation near the detector stability boundary. Measurements of {\alpha} indicate values substantially larger than expected, consistent with the sharper superconducting transitions introduced by the inverted TES fabrication process adopted for BA2-150 and BA3-220/270 detectors. Operational mitigation strategies were investigated through both increased multiplexing rates and elevated focal-plane operating temperatures. Faster multiplexing reduces aliasing by shifting the multiplexing Nyquist frequency beyond the excess noise roll-off, while elevated bath temperatures reduce TES electrical power and loop gain, improving detector stability and reducing NET by approximately 10%. These results demonstrate the importance of balancing TES responsivity, electrothermal stability, and multiplexed readout performance in next-generation CMB polarimeters.
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All authors S. Fatigoni, P. A. R. Ade, Z. Ahmed, M. Amiri, D. Barkats, R. Basu Thakur, C. A. Bischoff, D. Beck, J. J. Bock, V. Buza, B. Cantrall, J. R. Cheshire IV, J. Connors, J. Cornelison, M. Crumrine, A. J. Cukierman, E. Denison, L. Duband, M. A. Echter, M. Eiben, B. D. Elwood, J. P. Filippini, A. Fortes, M. Gao, C. Giannakopoulos, N. Goeckner-Wald, D. C. Goldfinger, S. Gratton, J. A. Grayson, A. Greathouse, P. K. Grimes, M. Halpern, S. Henderson, T. D. Hoang, J. Hubmayr, H. Hui, K. D. Irwin, M. Izquierdo Poza, J. H. Kang, K. S. Karkare, S. Kefeli, J. M. Kovac, C. Kuo, K. Lasko, K. Lau, M. Lautzenhiser, T. Liu, S. C. Mackey, N. Maher, K. G. Megerian, L. Minutolo, L. Moncelsi, Y. Nakato, H. T. Nguyen, R. O'Brient, S. N. Paine, A. Patel, M. A. Petroff, A. R. Polish, T. Prouve, C. Pryke, C. D. Reintsema, T. Romand, M. Salatino, A. Schillaci, B. Schmitt, B. Singari, A. Soliman, T. St. Germaine, A. Steiger, B. Steinbach, R. Sudiwala, K. L. Thompson, C. Tucker, A. D. Turner, C. Vergès, A. G. Vieregg, A. Wandui, A. C. Weber, J. Willmert, W. L. K. Wu, H. Yang, C. Yu, L. Zeng, C. Zhang, S. Zhang

Instrumentation and Detectors · Cross-listed from physics.optics

Effects of Quantum Noise and Source Blurring on Dark-Field Signal Retrieval in X-ray Speckle-Based Imaging

Hunwoo Lee, Jingcheng Yuan and Mini Das

X-ray speckle-based dark-field imaging offers high sensitivity to sub-pixel structural features, yet its quantitative reliability in clinical and preclinical settings remains constrained by low photon flux and finite focal spot sizes. However, how hardware-induced noise and source blurring propagate through retrieval algorithms to degrade signal integrity is not fully understood. Here, we systematically evaluate algorithm robustness quantified by signal linearity, sensitivity, and bias under photon starvation and source blurring across two mathematically distinct frameworks: differential-based intrinsic tracking (Low-Coherence System, LCS) and patch-wise explicit tracking (X-ray Speckle-Tracking Speckle-Vector-Tracking, XST-XSVT). Our experimental results demonstrate that input speckle pattern distortions propagate through retrieval algorithms in fundamentally different ways depending on algorithm architecture. As an example, using our setup, under severe photon starvation, derivative noise amplification in LCS causes its dark-field signal linearity and sensitivity to drop precipitously, while sharply elevating baseline bias. In contrast, XST-XSVT restricts these losses for sensitivity while maintaining a stable baseline, as its patch-wise variance calculation inherently suppresses stochastic noise. Similarly, under blur-limited conditions , source blurring washes out the speckle pattern, directly reducing dark-field sensitivity for both LCS and XST-XSVT. This characterization establishes operational boundaries for low-power and low-coherence X-ray systems, guiding algorithm selection and framework optimization to realize quantitative dark-field imaging in preclinical and clinical applications.
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Instrumentation and Detectors

Fabrication and validation of a MEMS Electron Monochromator

M.J. Adriaans, J.P. Hoogenboom and A. Mohammadi-Gheidari

Electron monochromators are essential components for many applications in electron microscopy but are often large and complex to operate instruments. In prior work, we presented a concept for monochromation using the fringe fields around miniature electrostatic elements. This concept could be realized with a compact monochromator design that requires tuning of only 7 power supplies. In this manuscript, we present the fabrication using MEMS technology and experimental testing of such a miniaturized monochromator. The fabrication scheme involves Bosch deep reactive ion etching to shape lens and deflector electrodes and focused ion beam milling to create nanoscale apertures in a silicon nitride membrane. All elements are then coated, precisely aligned and, after stacking, wire bonded to connect to external power supplies. We use the assembled prototype to measure the electron-beam energy spread in a scanning electron microscope demonstrating the energy filtering capability of the device. These results highlight the possibilities for making miniaturized electron optics instruments using alignment and stacking of different MEMS fabricated elements, representing an important step towards the development of compact, lightweight, high performance electron-beam instrumentation.
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Instrumentation and Detectors

Calibration of the discriminator threshold of the Amplifier-Shaper-Discriminator Chip for the Upgrade of the ATLAS Muon Drift-Tube Chambers for the High-Luminosity LHC

Oliver Kortner, Nick Meier and Julia Okfen

The read-out electronics of the ATLAS muon drift-tube chambers will be upgraded for operation at the High-Luminosity Large Hadron Collider. Part of the upgrade is the introduction of new amplifier-shaper-discriminator chips. This note presents the calibration of the discriminator threshold of the new chip in terms of primary electron signals using data from small-diameter muon drift-tube chambers operated in a monoenergetic, high-energy muon beam. The discriminator threshold intended for use in the ATLAS muon spectrometer corresponds to the signal of 20 primary electrons.
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Instrumentation and Detectors

Photogrammetry for Precise, Rapid Module Alignment in the Mu2e Tracker

Dylan Palo, Mamta Jangra, Aseet Mukherjee et al. (+1 more)

We discuss a photogrammetry technique to measure the inter-module alignment in the Mu2e tracker. The tracker consists of 216 modules each with 96 straw tubes. The relative alignment of the straw tubes in a module was previously measured by an X-ray technique, which tied the straw tube measurements to three fiducials per module. The photogrammetry technique uses an array of 15 cameras to make precise position measurements of the module fiducials in a global tracker coordinate system. Measurements of the fiducial position and radius on the camera's CCD yield ~$25 \mu m$ resolution in the transverse directions and < $300 \mu m$ along the camera axis. In addition, we describe a procedure to combine the images with "local" mechanical measurements to yield $<100 \mu m$ precision along the camera axis. The technique offers a touch-less, rapid (~1 hour), and affordable metrology approach within the requirements of the tracker.
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All authors Dylan Palo, Mamta Jangra, Aseet Mukherjee, Klara Northrup

Monday 24 August

Instrumentation and Detectors

Post-diffusion cooling effects on Hall-derived active lithium donor profiles in high-purity germanium

Kunming Dong, Dongming Mei, Anupama Karki et al. (+2 more)

Lithium (Li) diffusion is commonly used to form $n^{+}$ contacts in high-purity germanium (HPGe) detectors, but the final electrically active donor profile can be sensitive to the post-diffusion thermal history. Li was introduced into HPGe coupons using a lithium-in-oil suspension and diffused for $30~\mathrm{min}$ at nominal temperatures of $240$–$310~^{\circ}\mathrm{C}$. Short- and long-cooling protocols were documented by measured witness-Ge cooling histories. Sequential material removal combined with Hall-effect measurements at $77~\mathrm{K}$ was used to reconstruct difference-derived apparent Hall donor profiles. Because Hall response in a nonuniform conducting layer is mobility weighted, these profiles are operational electrically active-donor metrics rather than direct local or total-Li concentration profiles. Complementary-error-function fits were used to obtain the extrapolated apparent intercept $N_{s,\mathrm{app}}$ and the apparent profile-width parameter $D_{\mathrm{app}}$. For the coupons studied, short cooling was associated with larger $N_{s,\mathrm{app}}$ and sharper profiles, whereas long cooling was associated with lower $N_{s,\mathrm{app}}$ and broader low-concentration tails. Fit-derived concentration-threshold depths likewise extended farther into the Ge bulk for the long-cooling coupons. These results show that the complete post-diffusion thermal history should be considered when parameterizing Hall-active Li-diffused $n^{+}$ contacts for HPGe detector fabrication.
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All authors Kunming Dong, Dongming Mei, Anupama Karki, Partrick Burns, Sanjay Bhattarai

Instrumentation and Detectors

Performance Evaluation of a High-Granularity LYSO-SiPM-Based Position-Sensitive Detector for a One-Shot Gamma-Scanning System with Sub-Millimeter Spatial Resolution

Katyayni Tiwari, Arzoo Sharma, Jürgen Gerl et al. (+5 more)

A compact position-sensitive {\gamma}-detector based on a thin monolithic LYSO crystal and a 96-channel SiPM array is developed for the spatial characterization and calibration of segmented {\gamma}-ray detector systems used in nuclear-physics experiments. The detector is designed to provide localized irradiation and rapid two-dimensional response mapping. A 7 cm diameter and 3 mm thick LYSO crystal is optically coupled to the SiPM array, and the position of the incident {\gamma}-ray interaction is reconstructed from the relative scintillation-light signals collected by neighboring SiPM channels. An asymmetry-based charge-sharing method is employed to determine the interaction position from the spatial distribution of the detected scintillation light. Detailed GEANT4 simulations, including optical photon transport, were performed to investigate the detector response and estimate its intrinsic spatial resolution. The simulations predict a spatial resolution of approximately 0.5 mm for 60 keV and 511 keV {\gamma}-rays under idealized conditions. A prototype detector was developed and experimentally characterized using coincidence measurements with the {\gamma}-scanning facility at GSI, Germany. The experimental measurements demonstrate a spatial resolution better than 1 mm in the central detector region, while the position-dependent response and degradation near the detector boundaries are investigated. The experimental results are compared with GEANT4 predictions to identify the contributions of optical photon transport, charge sharing, and detector geometry to the measured spatial resolution. The developed detector provides a compact solution for the three-dimensional characterization of highly segmented {\gamma}-ray detector arrays in nuclear physics experiments.
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All authors Katyayni Tiwari, Arzoo Sharma, Jürgen Gerl, Ivan Kojouharov, P. Herrmann, H. Schaffner, G. Aggez, Pushpendra P. Singh

Instrumentation and Detectors

A Cosmic Muon Tomography System with Machine Learning based Momentum Measurement for Multi-Object Reconstruction and Material Characterization

Bharat Kumar Sirasva, Rohit Gupta and Satyajit Jena

Cosmic muon tomography is a powerful non-destructive imaging technique for inspecting dense and shielded materials through multiple Coulomb scattering. In this work, we present the design, simulation, and performance evaluation of a complete muon tomography system comprising six scintillator-strip tracking stations for trajectory reconstruction and a four-station magnetic spectrometer for muon momentum estimation. The detector geometry is implemented in the GEANT4 framework and optimized for object localization and material characterization. The reconstructed momentum is combined with the scattering angle to define the scattering density $\rho_s = {(\theta p)^2}/{L_{\mathrm{eff}}}$, which enhances sensitivity to material-dependent scattering. Point-of-Closest-Approach (PoCA) reconstruction is used to estimate scattering locations within the imaging volume. To detect and separate multiple unknown objects, Hierarchical Density-Based Spatial Clustering of Applications with Noise (HDBSCAN) is applied to the reconstructed PoCA cloud. Cluster-level scattering and geometric features are then extracted for object characterization. The proposed framework enables object detection, localization, volume estimation, shape reconstruction, and material ranking within a unified analysis pipeline. Simulation studies with multiple objects of different compositions demonstrate accurate reconstruction of object positions and geometries, while providing reliable material discrimination based on scattering density. The developed system offers a scalable approach for next-generation cosmic muon tomography applications in security screening, nuclear waste characterization, and non-destructive inspection.
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Sunday 23 August

Instrumentation and Detectors

Impact of Environmental Stress on Low Gain Avalanche Diode Sensors Response

Mohamed Hijas Mohamed Farook, Gaetano Barone, Diallo Boye et al. (+9 more)

Low Gain Avalanche Diodes or LGADs are silicon sensors capable of achieving excellent timing resolution due to their characteristic internal gain. Detectors based on LGAD technology play a crucial role in High Energy and Nuclear Physics experiments, among other applications. However, their performance is affected by environmental factors such as temperature, humidity, and storage conditions. A systematic evaluation of the response of LGAD sensors as a function of these environmental parameters is therefore of essential importance for any application. LGAD sensors fabricated at the Brookhaven National Laboratory are characterized and stress-tested against various operating conditions, such as rapid temperature and humidity changes. Dedicated and detailed simulations are used to interpret the experimental results.
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All authors Mohamed Hijas Mohamed Farook, Gaetano Barone, Diallo Boye, Gabriele D'Amen, Gabriele Giacomini, Timo Peltola, Jennifer Roloff, Enrico Rossi, Trevor Russell, Sally Seidel, Alessandro Tricoli, Lixing Wang

Saturday 22 August

Instrumentation and Detectors

An integrated micro-thermometer for mid-infrared photothermal spectroscopy of dense materials built in a CMOS 200 mm pilot line

Sandy Mathew, Sonia Messaoudène, Adrien Poizat et al. (+6 more)

Indirect photothermal infrared spectroscopy of dense materials typically relies on photoacoustic cells for detecting acoustic waves generated by light-induced heating. This detection approach can be challenging to implement as it is highly sensitive to the sealing quality of the interface between the cavity and the sample, as well as to the properties of the gas within the cavity. Here, we present a simplified and more robust method. This approach relies on direct photothermal temperature measurement using an optimized platinum microsensor fabricated on a thin silicon substrate that acts as a thermally transparent interface with the sample. The sensor design, fabrication in a 200 mm CMOS pilot line, assembly on a readout PCB, and experimental characterization are reported. The component achieves a signal-to-noise ratio close to 1000 making it well-suited for miniaturized and embedded infrared spectroscopic applications.
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All authors Sandy Mathew, Sonia Messaoudène, Adrien Poizat, Éléa Bourliaud, Marion Volpert, Jules Skubich, Stanislas Lhomme, Bertrand Bourlon, Kevin Jourde

Instrumentation and Detectors · Cross-listed from cs.LG

How Architecture and Training Affect TPC Representations Across Experiments

Tyler Wheeler, Michelle P. Kuchera, Raghuram Ramanujan et al. (+12 more)

Deep-learning efforts have increasingly shifted toward foundation model approaches. In experimental physics, this allows models and learned representations to be reused beyond the experiments in which they were developed. This work evaluates the reusability of representations across experiments and detector systems using probes on frozen encoders. These probes reveal task-relevant structure before downstream adaptation, complementing fine-tuning. Together with random-weight controls, they distinguish contributions from architecture and encoder training that downstream performance alone cannot resolve. Time projection chamber (TPC) data provide a useful testbed because events from TPC systems can be represented as variable-length sparse tensors, while detector geometries, event topologies, and scientific tasks can differ substantially. We investigate whether fixed-dimensional TPC event representations can be reused across classification tasks, experiments, and detector systems. Sparse ResNet and PointNet-style encoders produce 512-dimensional embeddings for four datasets from the GADGET II TPC and AT-TPC. Randomly initialized encoders isolate the contribution from architecture before supervised training. We then train each encoder on a classification task, freeze its parameters, and train a linear or nonlinear probe for each downstream task. We find that this architecture-induced structure remains useful across experiments and detector systems. The randomly initialized PointNet-style representation is highly informative on several tasks. The two architectures organize their embedding spaces differently, but neither exhibits a large, systematic loss of utility cross-detector. These results show that architecture is a major source of task-relevant structure in TPC embeddings and should be treated explicitly when assessing representation learning and developing reusable detector models.
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All authors Tyler Wheeler, Michelle P. Kuchera, Raghuram Ramanujan, William Sieland, Ryan Krupp, Yassid Ayyad, Daniel Bazin, Connor L. Cross, Hoi Yan Ian Heung, Andrew J. Jones, Ruchi Mahajan, Saiprasad Ravishankar, Pranjal Singh, Benjamin Votaw, Chris Wrede

Friday 21 August

Instrumentation and Detectors · Cross-listed from hep-ex

Hadronic Mono-Z Dark Matter Sensitivity with Flow Matching on CMS Open Data

Hitesh Rasineni and Bhavishya Chebrolu

We present a projected sensitivity study for hadronic mono-$Z$ dark-matter production using CMS Run~2015D HTMHT open data corresponding to 2.256382381~\invfb, from which 1{,}439{,}523 events satisfy the hadronic mono-$Z$ selection. Backgrounds are modelled with a conditional flow-matching continuous normalizing flow trained on the selected HTMHT events and evaluated on a held-out validation split reweighted to the full selected population. To mitigate artifacts from missing-object features and avoid in-sample scoring bias we apply sentinel imputation for undefined angular features, persist the train/validation split indices, and enforce a minimum reported background yield of 20 events when selecting the working point. A signal-side offline trigger proxy is applied to the simulated signal before scoring. Under this procedure the baseline analysis yields expected significances of 2.89$\sigma$, 7.62$\sigma$, and 7.41$\sigma$ for three simplified-model benchmarks. An ablation study that removes the detailed extra-jet kinematics reduces the expected significance by 53–71%, indicating that extra-jet topology carries substantial discriminating power in the hadronic mono-$Z$ channel. These results are projected sensitivities (no unblinding performed); the limitations and reproducibility of the study are discussed in Sections limitations and reproducibility.
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