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Physics High Energy Physics (Experiment)

hep-ex Watch High Energy Physics (Experiment)

Saturday 5 September

High Energy Physics (Experiment) · Cross-listed from hep-ph

On the analytic continuation and matching of threshold singularities from Vacuum Amplitudes

Selomit Ramírez-Uribe, Prasanna K. Dhani, German F.R. Sborlini et al. (+1 more)

We provide a detailed discussion for all kinematical configurations of the analytic continuation to negative values of initial-state on-shell energies used to generate interferences of scattering amplitudes from vacuum amplitudes in the Loop-Tree Duality. We also extend previous discussions on the matching of threshold singularities and introduce angular averaging as an efficient strategy to achieve a local cancellation when the matching of threshold singularities from vacuum amplitudes is constrained by flavour.
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All authors Selomit Ramírez-Uribe, Prasanna K. Dhani, German F.R. Sborlini, Germán Rodrigo

High Energy Physics (Experiment) · Cross-listed from hep-ph

Inelastic dark matter and baryon flavor symmetry in light of LUX-ZEPLIN (LZ) experiment

Hyun Min Lee

We present a novel model for inelastic dark matter in a simple extension of the Standard Model (SM) with a local $U(1)'$ baryon flavor symmetry, such as $U(1)_{B_i-B_j}$ with $i\neq j$. In this framework, we realize a realistic flavor structure for the mixing Yukawa couplings due to higher dimensional operators or renormalizable couplings between the SM quarks and extra vector-like quarks that are anomaly-free by themselves. We regard a Dirac singlet fermion as being dark matter and obtaining a small mass splitting for inelastic dark matter, only after the $U(1)'$ symmetry is broken spontaneously. We show that there is a consistent parameter space for explaining both the LZ nuclear recoil event and the correct relic density for dark matter and the existing collider and indirect detection bounds are satisfied at the same time. In this case, we predict a relatively light $Z'$ boson with $10-20\,{\rm GeV}$ mass and a weak gauge coupling, suggesting a dedicated search at colliders. The future data with higher recoil energies at direct detection experiments will play a decisive role of discriminating between the scenarios of light and heavy dark matter.
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High Energy Physics (Experiment) · Cross-listed from physics.ins-det

Simulation Study of the Design and Spatial Resolution of a Novel AC-coupled Cross Strip LGAD

Jingkang Xu, Mengzhao Li, Zhiliang Hu et al. (+5 more)

AC-coupled Low Gain Avalanche Diode (AC-LGAD), evolved from the standard LGAD technology, are silicon detectors characterized by exceptional temporal and spatial resolutions. This work proposes a novel sensor named AC-coupled Cross Strip LGAD (CS-LGAD) structure with dual-layered overlapping strip electrodes. It can achieve two-dimensional particle position measurement with low readout density while also inheriting the high temporal resolution of the LGAD. The sensor structure, doping and current-voltage (I-V) characteristics of the sensor were investigated through TCAD simulations. Additionally, Monte Carlo simulations were employed to simulate the signal response of CS-LGAD to minimum ionizing particles (MIPs). The response of MIPs hitting different positions was simulated, and the reconstruction of particle coordinates (x and y) was achieved based on the sharing of charges on the dual-layer electrodes. The spatial resolution might reach 3.6% and 5.5% of the pitch size in the x and y directions, respectively, according to the simulation. The proposed CS-LGAD is a promising 4D detector with low mass and low readout density.
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All authors Jingkang Xu, Mengzhao Li, Zhiliang Hu, Tianya Wu, Mei Zhao, Zhijun Liang, Lihua Mo, Tianjiao Liang

High Energy Physics (Experiment) · Cross-listed from physics.ins-det

Long-term performance of non-ALD MCP-PMTs in the high-radiation environment of ALICE

Yury Melikyan for the ALICE Collaboration

The Fast Interaction Trigger detector of the ALICE apparatus at the LHC includes a Cherenkov subsystem utilizing 52 Planacon XP85002/FIT-Q microchannel plate-based photomultiplier tubes. It is a precise trigger, multiplicity and luminosity detector located in the forward region, where the flux of collision products is the largest. The photon load reaches up to 2*10^8 photoelectrons / cm^2 / s for the innermost photosensors, corresponding to 0.4 {\mu}A / cm^2 average anode current density. The lifetime-extended version of the Planacon MCP-PMT with atomic layer deposition cannot handle such a large anode current. We therefore use the non-ALD version of the Planacons that, on the other hand, suffer from a limited lifetime in terms of the integrated anode charge. Here we present the long-term performance trends of the non-ALD Planacons up to the integrated anode charge of 2 C / cm^2. We demonstrate that the low-gain operation strategy allows to maintain excellent time resolution in multiphoton mode unchanged up to that large integrated charge. While the majority of the equally illuminated MCP-PMTs feature almost identical ageing speed, two outliers suffering from a faster ageing coincide with the outliers in the noise characteristics measured prior to the irradiation. Moreover, we report that the effective ageing speed is partially suppressed by the self-recovery of the response of aged MCP-PMTs newly observed by our group during months-long no-beam periods.
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High Energy Physics (Experiment)

Prospective study of light dark matter search in positron beam mode with DarkSHINE experiment initiative

Xu-Liang Zhu, Haidar Mas'ud Alfanda, Shu Li et al. (+4 more)

We perform the prospective study on searching for invisibly decayed dark photons ($A^{\prime}$) in positron-on-fixed-target (POT) scheme with the DarkSHINE experiment simulation setup. In the positron-on-fixed-target scheme, two additional production channels of dark photons via annihilation with extranuclear electrons are present: non-resonant t-channel ($e^+e^-N \to \gamma A^{\prime}N$) and resonant s-channel ($e^+e^-N \to A^{\prime}N$), alongside bremsstrahlung emission similar to electron-on-fixed-target scheme. Based on a GEANT4 full detector simulation of an 8 GeV positron beam with $3 \times 10^{14}$ POT events, we developed an analysis strategy using missing energy and momentum signatures across three orthogonal signal regions optimized for these channels. Our results indicate that the additional annihilation channels of dark photon production enhance the dark photon invisible decay search sensitivity, improving the exclusion limits by approximately two orders of magnitude compared to previous constraints in the electron-on-fixed target (EOT) scheme, particularly near the center-of-mass energy threshold for annihilation production of dark photons.
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All authors Xu-Liang Zhu, Haidar Mas'ud Alfanda, Shu Li, Kun Liu, Tong Sun, Haijun Yang, Yi-Fan Zhu

High Energy Physics (Experiment)

Measurement of CP Asymmetry Parameters and Polarization Correlations in $\Omega^{-}\bar{\Omega}^{+}$ Pairs

BESIII Collaboration: M. Ablikim, M. N. Achasov, P. Adlarson et al. (+776 more)

Using $(2.71 \pm 0.01) \times 10^9$ $\psi(3686)$ events collected with the BESIII detector, a joint full angular distribution analysis is carried out for the process $\psi(3686) \to \Omega^-(\to\Lambda K^-) \, \bar{\Omega}^{+}(\to \bar{\Lambda}K^+)$. The first simultaneous measurement of the weak decay parameters $\phi_{\Omega^{-}}$ and $\phi_{\bar{\Omega}^{+}}$ for $\Omega^- \to K^-\Lambda$ and $\bar{\Omega}^+ \to K^+\bar{\Lambda}$ is performed, yielding the first result for the CP-sensitive observable, $\phi_{\rm CP} = (-0.004 \pm 0.055 \pm 0.017)~\text{rad}$, where the first and second uncertainties are statistical and systematic, respectively. This further enables the extraction of the weak and strong phase differences between the $P$- and $D$-wave amplitudes: $(\xi_D - \xi_P) = (-0.15 \pm 2.25 \pm 0.69)~\text{rad}$ and $(\delta_D - \delta_P) = (-0.97 \pm 0.88 \pm 0.34)~\text{rad}$. Additionally, the polarization correlations between $\Omega^{-}$ and $\bar{\Omega}^{+}$ are measured.
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All authors BESIII Collaboration: M. Ablikim, M. N. Achasov, P. Adlarson, X. C. Ai, C. S. Akondi, R. Aliberti, A. Amoroso, L. P. An, Q. An, M. S. Anderson, Y. Bai, O. Bakina, H. R. Bao, X. L. Bao, M. Barbagiovanni, V. Batozskaya, K. Begzsuren, N. Berger, M. Berlowski, M. B. Bertani, D. Bettoni, F. Bianchi, E. Bianco, A. Bortone, I. Boyko, R. A. Briere, A. Brueggemann, D. Cabiati, H. Cai, M. H. Cai, X. Cai, A. Calcaterra, G. F. Cao, N. Cao, X. Cao, S. A. Cetin, X. Y. Chai, J. F. Chang, T. T. Chang, G. R. Che, Y. Z. Che, C. H. Chen, Chao Chen, G. Chen, H. S. Chen, H. Y. Chen, J. D. Chen, M. L. Chen, S. J. Chen, S. M. Chen, T. Chen, W. Chen, X. R. Chen, X. T. Chen, X. Y. Chen, Y. B. Chen, Y. Q. Chen, Z. K. Chen, J. Cheng, L. N. Cheng, S. K. Choi, X. Chu, G. Cibinetto, F. Cossio, J. Cottee-Meldrum, H. L. Dai, J. P. Dai, X. C. Dai, A. Dbeyssi, R. E. de Boer, D. Dedovich, Z. Y. Deng, A. Denig, I. Denisenko, M. Destefanis, F. De Mori, E. Di Fiore, X. X. Ding, Y. Ding, J. Dong, L. Y. Dong, M. Y. Dong, Z. J. Dong, K. B. Du, M. C. Du, S. X. Du, Shaoxu Du, X. L. Du, Y. Q. Du, C. D. Duan, Z. H. Duan, P. Egorov, G. F. Fan, K. X. Fan, Y. H. Fan, Z. F. Fan, J. Fang, Jin Fang, S. S. Fang, W. X. Fang, L. Fava, F. Feldbauer, G. Felici, C. Q. Feng, J. H. Feng, Q. X. Feng, Y. T. Feng, M. Fritsch, C. D. Fu, J. L. Fu, Y. W. Fu, Xu Gao, Y. Gao, Y. N. Gao, Yunong Gao, Z. Gao, S. Garbolino, I. Garzia, L. Ge, L. Q. Ge, P. T. Ge, C. Geng, A. Gilman, K. Goetzen, J. Gollub, J. B. Gong, J. D. Gong, L. Gong, W. X. Gong, W. Gradl, M. Greco, M. D. Gu, M. H. Gu, C. Y. Guan, S. Y. Guan, A. Q. Guo, H. Guo, J. N. Guo, L. B. Guo, M. J. Guo, R. P. Guo, X. Guo, Y. P. Guo, Z. Guo, A. Guskov, J. Gutierrez, J. Y. Han, T. T. Han, X. Han, F. Hanisch, J. Y. Hao, K. D. Hao, X. Q. Hao, F. A. Harris, C. Z. He, K. K. He, K. L. He, F. H. Heinsius, C. H. Heinz, Y. K. Heng, C. Herold, N. D. Hoffman, P. C. Hong, G. Y. Hou, X. T. Hou, Z. L. Hou, H. M. Hu, J. F. Hu, Q. P. Hu, S. L. Hu, T. Hu, Y. Hu, Y. X. Hu, Z. M. Hu, G. S. Huang, L. Q. Huang, P. Huang, X. T. Huang, Y. P. Huang, Y. S. Huang, T. Hussain, N. Hüsken, N. in der Wiesche, Q. Ji, Q. P. Ji, W. Ji, X. B. Ji, X. L. Ji, Y. Y. Ji, L. K. Jia, S. Jia, X. Q. Jia, D. Jiang, H. B. Jiang, S. J. Jiang, X. S. Jiang, Y. Jiang, J. B. Jiao, Z. Jiao, B. W. Jin, L. C. L. Jin, S. Jin, Y. Jin, M. Q. Jing, X. M. Jing, T. Johansson, S. Kabana, X. L. Kang, X. S. Kang, B. C. Ke, A. Khoukaz, O. B. Kolcu, S. H. Kong, B. Kopf, L. Kröger, L. Krümmel, Y. Y. Kuang, M. Kuessner, X. Kui, N. Kumar, A. Kupsc, W. Kühn, L. Y. Lan, Q. Lan, J. Y. Lee, T. T. Lei, M. Lellmann, T. Lenz, C. Li, C. H. Li, C. J. Li, C. K. Li, Cong Li, D. M. Li, F. Li, G. Li, H. B. Li, H. J. Li, H. N. Li, H. P. Li, Hui Li, J. N. Li, J. W. Li, K. Li, K. L. Li, L. J. Li, L. K. Li, Lei Li, M. H. Li, M. R. Li, M. T. Li, P. L. Li, P. R. Li, Q. M. Li, R. Li, S. X. Li, S. Y. Li, Shanshan Li, T. Li, T. Y. Li, W. D. Li, W. G. Li, X. Li, X. H. Li, X. K. Li, X. L. Li, X. Y. Li, X. Z. Li, Y. H. Li, Y. B. Li, Y. C. Li, Y. G. Li, Y. L. Li, Y. P. Li, Yi Li, Z. H. Li, Z. J. Li, Z. L. Li, Z. X. Li, Z. Y. Li, Zaiyi Li, C. Liang, H. Liang, Y. F. Liang, Y. T. Liang, Z. Z. Liang, G. R. Liao, L. B. Liao, M. H. Liao, Y. P. Liao, J. Libby, A. Limphirat, C. X. Lin, D. X. Lin, T. Lin, B. J. Liu, C. Liu, C. X. Liu, F. Liu, F. H. Liu, Feng Liu, G. M. Liu, H. Liu, H. B. Liu, H. M. Liu, Huihui Liu, J. B. Liu, K. Liu, K. Y. Liu, Ke Liu, Kun Liu, L. Liu, L. C. Liu, Lu Liu, M. H. Liu, P. L. Liu, Q. Liu, S. B. Liu, T. Liu, W. T. Liu, X. Liu, X. K. Liu, X. L. Liu, X. P. Liu, X. T. Liu, X. Y. Liu, Y. Liu, Y. B. Liu, Yi Liu, Z. A. Liu, Z. D. Liu, Z. Q. Liu, Z. X. Liu, Z. Y. Liu, X. C. Lou, H. J. Lu, J. G. Lu, X. L. Lu, Y. Lu, Y. H. Lu, Y. P. Lu, C. L. Luo, J. Q. Luo, J. R. Luo, J. S. Luo, M. X. Luo, Q. Q. Luo, T. Luo, X. L. Luo, XiaoRong Lv, Z. Y. Lv, X. R. Lyu, Y. F. Lyu, Y. H. Lyu, C. L. Ma, F. C. Ma, H. L. Ma, Heng Ma, J. L. Ma, L. L. Ma, Q. M. Ma, R. Q. Ma, T. Ma, X. T. Ma, X. Y. Ma, F. E. Maas, M. Maggiora, S. Maity, S. Malde, L. M. Mansur, Y. J. Mao, Z. P. Mao, S. Marcello, A. Marshall, F. M. Melendi, Z. X. Meng, G. Mezzadri, H. Miao, T. J. Min, T. Mineeva, S. W. Ming, R. E. Mitchell, X. H. Mo, A. F. Mohammed, B. Moses, N. Yu. Muchnoi, J. Muskalla, Y. Nefedov, F. Nerling, H. Neuwirth, Z. Ning, S. Nisar, Q. L. Niu, W. D. Niu, Y. Niu, C. Normand, S. L. Olsen, Q. Ouyang, I. V. Ovtin, S. Pacetti, X. Pan, Y. Pan, C. Y. Pang, A. Pathak, Y. P. Pei, Y. Y. Pei, M. Pelizaeus, G. L. Peng, H. P. Peng, X. J. Peng, Y. Y. Peng, K. Peters, K. Petridis, J. L. Ping, R. G. Ping, S. Plura, S. Polikarpov, V. Prasad, L. Pöpping, F. Z. Qi, H. R. Qi, L. Y. Qian, S. Qian, W. B. Qian, C. F. Qiao, J. H. Qiao, J. J. Qin, J. L. Qin, L. Q. Qin, L. Y. Qin, P. B. Qin, X. P. Qin, X. S. Qin, Z. H. Qin, J. F. Qiu, J. Rademacker, K. Ravindran, C. F. Redmer, Y. Ren, A. Rivetti, M. Rolo, G. Rong, S. S. Rong, F. Rosini, Ch. Rosner, M. Q. Ruan, W. R. Ruangyoo, N. Salone, A. Sarantsev, Y. Schelhaas, M. Schernau, K. Schoenning, M. Scodeggio, Jian Shan, W. Shan, X. Y. Shan, Z. J. Shang, J. F. Shangguan, L. G. Shao, M. Shao, C. P. Shen, H. F. Shen, W. H. Shen, X. Y. Shen, B. A. Shi, Ch. Y. Shi, H. Shi, J. L. Shi, J. Y. Shi, S. Shi, X. Shi, X. D. Shi, H. L. Song, J. J. Song, M. H. Song, T. Z. Song, W. M. Song, Y. Song, Y. X. Song, Zirong Song, S. Sosio, S. Spataro, S. Stansilaus, F. Stieler, M. Stolte, J. L. Su, S. S Su, G. B. Sun, G. X. Sun, H. Sun, H. K. Sun, J. F. Sun, K. Sun, L. Sun, R. Sun, S. S. Sun, W. Y. Sun, Y. C. Sun, Y. J. Sun, Y. S. Sun, Y. Z. Sun, Z. Q. Sun, Z. T. Sun, H. Tabaharizato, N. T. Tagsinsit, C. J. Tang, G. Y. Tang, H. Y. Tang, J. Tang, J. J. Tang, L. F. Tang, Y. A. Tang, Z. H. Tang, L. Y. Tao, M. Tat, J. X. Teng, J. Y. Tian, W. H. Tian, Y. Tian, K. Yu. Todyshev, I. Uman, E. van der Smagt, S. W. Wan, X. Wan, B. Wang, B. Q. Wang, Bin Wang, Bo Wang, C. Wang, C. L. Wang, Cong Wang, D. Y. Wang, F. K. Wang, H. J. Wang, H. R. Wang, J. Wang, J. H. Wang, J. J. Wang, J. P. Wang, K. Wang, L. L. Wang, M. Wang, Mi Wang, N. Y. Wang, S. Wang, Shun Wang, W. Wang, W. P. Wang, X. F. Wang, X. L. Wang, X. N. Wang, Xin Wang, Y. Wang, Y.-K. Wang, Y. D. Wang, Y. F. Wang, Y. H. Wang, Y. J. Wang, Y. L. Wang, Yanning Wang, Yaqian Wang, Yi Wang, Yuan Wang, Z. Wang, Z. L. Wang, Z. Q. Wang, Z. Y. Wang, Zhi Wang, D. Wei, D. H. Wei, D. J. Wei, H. R. Wei, F. Weidner, H. R. Wen, S. P. Wen, U. Wiedner, G. Wilkinson, J. F. Wu, L. H. Wu, L. J. Wu, S. G. Wu, S. M. Wu, X. W. Wu, Y. C. Wu, Z. Wu, H. L. Xia, L. Xia, B. H. Xiang, D. Xiao, G. Y. Xiao, H. Xiao, Y. L. Xiao, Z. J. Xiao, C. Xie, K. J. Xie, Y. Xie, Y. Xie, Y. G. Xie, Y. H. Xie, Z. P. Xie, T. Y. Xing, G. F. Xu, H. Y. Xu, Q. J. Xu, Q. N. Xu, X. P. Xu, Y. Xu, Y. C. Xu, Z. S. Xu, F. Yan, J. Z. Yan, L. Yan, W. B. Yan, W. C. Yan, W. H. Yan, X. Q. Yan, Y. Y. Yan, H. J. Yang, H. L. Yang, H. X. Yang, J. H. Yang, L. Y. Yang, N. Yang, R. J. Yang, X. Y. Yang, Y. Yang, Y. G. Yang, Y. H. Yang, Y. Q. Yang, Y. Z. Yang, Z. B. Yang, Z. W. Yang, W. J. Yao, Z. P. Yao, M. Ye, M. H. Ye, M. Y. Ye, Z. J. Ye, H. L. Yi, K. Yi, Junhao Yin, Qiqin Yin, X. Y. Yin, Z. Y. You, B. X. Yu, C. X. Yu, G. Yu, J. S. Yu, L. W. Yu, T. Yu, X. D. Yu, Yongchao Yu, C. Z. Yuan, H. Yuan, J. Yuan, Jie Yuan, L. Yuan, M. K. Yuan, S. H. Yuan, Y. Yuan, Z. Y. Yuan, C. X. Yue, Ying Yue, A. A. Zafar, F. R. Zeng, S. H. Zeng, Y. J. Zeng, Yujie Zeng, M. Z. Zhai, Y. C. Zhai, Y. H. Zhan, B. L. Zhang, B. R. Zhang, D. H. Zhang, G. Y. Zhang, Gengyuan Zhang, H. C. Zhang, H. H. Zhang, H. L. Zhang, H. Q. Zhang, H. R. Zhang, H. Y. Zhang, H. Z. Zhang, Han Zhang, J. Zhang, J. J. Zhang, J. L. Zhang, J. Q. Zhang, J. W. Zhang, J. Y. Zhang, J. Z. Zhang, Jianyu Zhang, Jiawen Zhang, Jin Zhang, Jiyuan Zhang, L. M. Zhang, Lei Zhang, N. Zhang, P. Zhang, Q. Y. Zhang, Q. Z. Zhang, R. Y. Zhang, Rui Zhang, S. H. Zhang, S. N. Zhang, Shulei Zhang, W.-C. Zhang, X. M. Zhang, X. Y. Zhang, Y. T. Zhang, Y. H. Zhang, Y. P. Zhang, Y. X. Zhang, Yao Zhang, Yu Zhang, Yu Zhang, Yu Zhang, Z. Zhang, Z. D. Zhang, Z. H. Zhang, Z. R. Zhang, Z. Y. Zhang, Zh. Zh. Zhang, Zhaoke Zhang, Zhilong Zhang, Ziyang Zhang, Ziyu Zhang, P. Zhang, G. Zhao, J.-P. Zhao, J. Y. Zhao, J. Z. Zhao, L. Zhao, Lei Zhao, M. G. Zhao, R. P. Zhao, Y. B. Zhao, Y. L. Zhao, Y. P. Zhao, Y. X. Zhao, Z. G. Zhao, A. Zhemchugov, B. Zheng, B. M. Zheng, J. P. Zheng, W. J. Zheng, W. Q. Zheng, X. R. Zheng, Y. H. Zheng, B. Zhong, C. Zhong, X. Zhong, H. Zhou, J. Q. Zhou, S. Zhou, X. Zhou, X. K. Zhou, X. R. Zhou, X. Y. Zhou, Y. X. Zhou, Y. Z. Zhou, A. N. Zhu, J. Zhu, J. J. Zhu, K. Zhu, K. J. Zhu, K. S. Zhu, Lin Zhu, S. H. Zhu, T. J. Zhu, W. D. Zhu, W. J. Zhu, W. Z. Zhu, Y. C. Zhu, Z. A. Zhu, X. Y. Zhuang, M. Zhuge, J. H. Zou, J. Zu

Friday 4 September

High Energy Physics (Experiment) · Cross-listed from physics.data-an

Continuous Event Weighting for Resonance Searches

Yi Yang, Jun-Jie Chang and Hao-Yin Liao

We develop a continuous event weighting framework for resonance searches that uses auxiliary event information without dividing the data into increasingly fine sensitivity categories. A hard selection is a binary weight, finite categories correspond to piecewise constant weights, and in the background dominated limit their fine partition approaches a continuous signal to background density ratio weight. The construction retains auxiliary discrimination in a single physically interpretable resonance spectrum, with calculable statistical variance and direct recovery of the selected signal yield. One million fully explicit event level pseudoexperiments using Gaussian, Gamma, and Beta auxiliary observables verify yield recovery, uncertainty propagation, and frequentist coverage while substantially improving discovery sensitivity. The method is further tested on publicly available CMS Run2016G and Run2016H diphoton Open Data as an independent real data benchmark, using detector level gluon fusion Higgs simulation only as the signal reference. This is a methodological test of the framework, not a CMS Higgs analysis. The results demonstrate a practical route to exploiting continuous auxiliary information without proliferating sensitivity driven event categories.
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High Energy Physics (Experiment) · Cross-listed from physics.ins-det

Kinematic Fitting of electromagnetic calorimeter data - an improved method

Nicolas Kolanus, Jonas Kohlen and Ulrike Thoma

Kinematic fitting is widely used in particle physics experiments as a powerful tool to improve experimental resolutions, to suppress background and to provide selection criteria for the identification of specific reactions. Kinematic fitting methods, however, typically assume that the fitted quantities follow Gaussian distributions; an assumption which does not always hold. This is particularly true for energy measurements from electromagnetic calorimeters. This issue can largely be overcome by performing a transformation of the non-Gaussian variables into variables which follow a Gaussian distribution. The new adapted kinematic fitting procedure allows to better account for the non-Gaussian nature of the measured calorimeter energies, at the same time improving the accuracy and robustness of the kinematic fit. This leads to improved pull and confidence-level distributions of the kinematic fit as well as improved invariant mass distributions and signal-to-background ratios in the final event sample.
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High Energy Physics (Experiment) · Cross-listed from physics.ed-ph

AI in Particle Physics Education: Research Problems and Foundational Skills

M. Mikhasenko, M. Stahl, I. Segal et al. (+3 more)

Generative AI can produce perfect solutions to standard physics homework, weakening the connection between submitted work and knowledge a student can use independently. We report a redesign of the introductory nuclear and particle physics course at Ruhr University Bochum, in which AI was permitted and encouraged alongside traditional tools on unusually difficult, research-shaped assignments. We found that most students remained engaged with the assignments throughout the course and produced ambitious work, while the course did not reliably secure its foundational objective. We offer this mixed experience as a reference point for discussion.
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All authors M. Mikhasenko, M. Stahl, I. Segal, D. Parmar, A. Zimmer, A. Kazatsky

High Energy Physics (Experiment) · Cross-listed from hep-ph

Agnostic search for a vector-like top partner at a lepton collider via the recoil mass technique

Higinio Valle, Cristina Oropeza Barrera and Oscar Ochoa-Valeriano

A study of the single production of a vector-like top partner $T$ at a $\sqrt{s}=3$ TeV $e^{+}e^{-}$ collider is presented, using a decay-mode and mass-agnostic event selection built around the recoil mass observable. The analysis relies on fully simulated samples processed through a common reconstruction and event selection chain. The baseline selection is validated without beam polarization or initial-state radiation (ISR). The impact of more realistic running conditions, including ISR together with an $e^{-}$ beam polarization of $-80\%$, is then evaluated and the discovery reach is mapped as a function of the top partner mass $m_{T}$ and coupling strength $\kappa_{T}$. In the baseline scan, the estimated statistical significance rises above $3\sigma$ for the lowest benchmark masses once $\kappa_{T}$ exceeds approximately 0.3.
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High Energy Physics (Experiment) · Cross-listed from hep-ph

The Colors of Jet Quenching

Hannah Bossi, Maxence Larose and Yacine Mehtar-Tani

We combine inclusive jet nuclear modification factors with energy-energy correlators to perform a data-driven extraction of the quark and gluon quenching factors and the medium resolution scale from the small-angle region. Taking coherent energy loss as a null hypothesis, we find jet quenching factors incompatible with Casimir scaling. Incorporating color decoherence through antenna energy loss improves the description of the data and restores Casimir scaling, providing evidence that the quark-gluon plasma partially resolves the internal structure of jets in heavy-ion collisions.
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High Energy Physics (Experiment) · Cross-listed from hep-ph

Displaced Signals from Long-lived Particles in Neutrinoless Double Beta Decay

Patrick D. Bolton, Noor-Inès Boudjema, Frank F. Deppisch et al. (+2 more)

Much of the literature on neutrinoless double beta ($0\nu\beta\beta$) decay with light new-physics mediators focuses on invisible missing energy. We investigate the scenario in which a massive Majoron-like particle $\phi$ is produced on-shell during $0\nu\beta\beta$ decay and subsequently decays into visible final states after travelling a macroscopic distance. Specifically, we analyze the displaced energy deposition from $\phi$ decays into a photon pair ($\gamma\gamma$), a photon and a dark photon ($\gamma\gamma_D$) and an electron-positron pair ($e^+e^-$). We demonstrate that the displaced decays modify the expected visible energy spectra and provide novel, distinct experimental signatures at current and upcoming $0\nu\beta\beta$ experiments, with the promise of improving the sensitivity of the standard invisible Majoron searches in $0\nu\beta\beta$ decay by more than two orders of magnitude. The relevant effective couplings can naturally arise in well-motivated ultraviolet-complete scenarios that conventional $0\nu\beta\beta$ decay searches cannot probe.
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All authors Patrick D. Bolton, Noor-Inès Boudjema, Frank F. Deppisch, Chandan Hati, Chayan Majumdar

High Energy Physics (Experiment) · Cross-listed from hep-ph

Inelastic from the Other Side: Xenon Excitation Signals in Light of the LZ High-Recoil Event

Guanhua Gu, Lingfeng Li, Shao-Song Tang et al. (+1 more)

The LUX-ZEPLIN (LZ) experiment recently reported a single event consistent with a nuclear recoil of $E_{\rm NR}\sim248\pm23\,(\mathrm{stat})\pm23\,(\mathrm{syst})$~keV in an extended-energy search. We study the accompanying inelastic-xenon channel, $\chi+\Xe\to\chi+\Xe^{*}$, which provides a complementary test of DM interpretations of such high-recoil events. Using the non-relativistic effective-field-theory (NREFT) framework with shell-model nuclear-transition inputs, we compute the inelastic-xenon rates for representative scenarios including inelastic dark matter and accelerated DM populations. We also simulate their S1–S2 responses, with detector modeling validated against public LZ data. The nuclear de-excitation adds an electromagnetic component shifting the signal toward the electronic-recoil band and, in some cases, toward clustered backgrounds from isotopes. We therefore construct a schematic, physics-motivated background model and perform a simplified statistical analysis. For many benchmarks, the inelastic-xenon rate is $\mathcal{O}(0.1)$ of the elastic rate or below, suggesting that substantially larger exposures are required before this companion channel becomes observable. Our results illustrate the importance of isotope-induced background structures in the extended-energy region and extend the phenomenology of inelastic-xenon signatures to a wider range of DM scenarios.
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All authors Guanhua Gu, Lingfeng Li, Shao-Song Tang, Yongheng Xu

High Energy Physics (Experiment) · Cross-listed from hep-ph

New measurements in leptonic kaon and pion decays: experimental and theoretical perspectives

Lukas Allwicher, Stefan Alexandru Ghinescu, Federico Mescia et al. (+2 more)

We study the future prospects for precision measurements of purely leptonic charged-current kaon and pion decays. Together with the ratio of leptonic widths $R_K^\nu=\Gamma(K\to e\nu)/\Gamma(K\to\mu\nu)$, we consider the single ratios $R_{K\pi}^{\ell=\mu,e} = \Gamma(K \to \ell\nu) / \Gamma(\pi \to \ell\nu)$, for which many experimental uncertainties cancel, as well as the double ratio $R_{K\pi}^e / R_{K\pi}^\mu$, which provides a particularly sensitive probe of new physics. This study is timely in light of two converging developments. On the experimental side, a new conceptual design for a dedicated setup based on a slow-extracted proton beam and a multi-year data-taking program, is expected to achieve a precision at the few $10^{-4}$ level. On the theory side, recent lattice-QCD calculations have reached a comparable level of accuracy. Finally, we assess the impact of these next-generation measurements on searches for physics beyond the Standard Model and show that they can provide constraints that are either competitive with or complementary to existing bounds.
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All authors Lukas Allwicher, Stefan Alexandru Ghinescu, Federico Mescia, Tommaso Spadaro, Lucine Tabatt

High Energy Physics (Experiment) · Cross-listed from hep-ph

Exothermic Dark Matter at LZ

Carlos Henrique de Lima

We investigate whether the high-energy nuclear recoil reported by the LUX-ZEPLIN (LZ) experiment can be explained by exothermic dark matter. We realize this framework in a minimal inelastic dark photon model and show that both freeze-out and low-reheating-temperature freeze-in cosmologies can reproduce the observed rate, with GeV-scale mediator masses and small kinetic mixing. We find that the LZ event can occur in a preferred parameter region with dark matter mass around $m_\chi \sim 30-200~\mathrm{GeV}$, and mass splitting $\delta \sim 0.5-1~\mathrm{MeV}$. The scenario is largely insensitive to halo uncertainties and has robust predictions for different targets. In particular, argon and germanium detectors are expected to observe events at energies above the current xenon window.
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High Energy Physics (Experiment) · Cross-listed from hep-ph

The axial-vector nucleon form factor in the meson dominance picture: the role triangle singularities from a dispersive view

Enrique Ruiz Arriola and Pablo Sanchez-Puertas

The nucleon axial form factor is analyzed in terms of a dispersion relation comprising chiral perturbation theory (ChPT) and perturbative QCD (pQCD) in the low- and high-momentum regimes respectively, which implies a set of superconvergence sum rules for the $A \to N \bar N$ spectral function. In the timelike region below the $N \bar N$ production threshold we include the $a_1$ and $a_1'$ resonances, with finite-width effects modeled through $\rho \pi$ and $\sigma \pi$ intermediate states. Above the $N \bar N$ threshold, we model an infinite tower of radially excited $1^{++}$ resonances with a non-integer power fall-off, eventually matching pQCD. In this setup, we find that both the ChPT and pQCD contributions are tiny. In turn, the dominant $\rho\pi$ triangle provides the leading deviations from axial meson dominance. Our calculation is not a fit; it contains parameters with a priori uncertainties estimates. The axial radius is predicted to be $r_A^2 =(0.28-0.33)~\textrm{fm}^2 = ( 0.47-0.57~\textrm{fm})^2$ in agreement with recent lattice QCD results but inconsistent with the MINER$\nu$A determination. A simple semiempirical formula is provided accounting for the main physical effects.
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High Energy Physics (Experiment) · Cross-listed from hep-ph

Higgs Boson Pair Production via Gluon Fusion: Higher-Order Corrections and Theoretical Uncertainties

Ajjath A H, Simone Alioli, Emanuele Bagnaschi et al. (+51 more)

In this contribution, the higher-order QCD and electroweak corrections to Standard Model Higgs boson pair production via the gluon-fusion mechanism, $gg\to hh$, are summarized and the different sources of theoretical uncertainty are assessed. The discussion includes finite top quark mass effects, matching to parton showers, approximate NNLO and N$^3$LO QCD corrections, NLO electroweak effects, and uncertainties associated with the top quark mass scheme and perturbative scale choices. In addition, we provide an updated state-of-the-art recommendation for the inclusive gluon-fusion Higgs boson pair production cross section and the corresponding Higgs boson pair invariant-mass distribution.
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All authors Ajjath A H, Simone Alioli, Emanuele Bagnaschi, Arunima Bhattacharya, Huan-Yu Bi, Roberto Bonciani, Marco Bonetti, Francisco Campanario, Sauro Carlotti, Jamie Chang, Long-Bin Chen, Xuan Chen, Yuesheng Dai, Joshua Davies, Giuseppe Degrassi, Pier Paolo Giardino, Massimiliano Grazzini, Ramona Gröber, Gudrun Heinrich, Li-Hong Huang, Rui-Jun Huang, Sebastian Jaskiewicz, Stephen Jones, Stefan Kallweit, Matthias Kerner, Hai Tao Li, Shi-Yuan Li, Jonas M. Lindert, Yan-Qing Ma, Giulia Marinelli, Javier Mazzitelli, Margarete Mühlleitner, Davide Napoletano, Philipp Rendler, Jonathan Ronca, Johannes Schlenk, Kay Schönwald, Hua-Sheng Shao, Michael Spira, Thomas Stone, Daniel Stremmer, Robert Szafron, William J. Torres Bobadilla, Yannick Ulrich, Augustin Vestner, Marco Vitti, Jian Wang, Huai-Min Yu, Hantian Zhang, Fabio Monti, Arantxa Ruiz Martínez, Angela Taliercio, Andreas Papaefstathiou, Ludovic Scyboz

High Energy Physics (Experiment) · Cross-listed from hep-ph

Flavor Tomography of Long-Lived Neutrino-Mass Mediators: Probing the Neutrino Mass Ordering at the HL-LHC

Renjie Wang

The neutrino mass ordering remains unresolved because long-baseline oscillation measurements are entangled with the unknown CP phase $\delta_{CP}$; a collider probe free of this degeneracy would provide a qualitatively different, complementary test. We show that when the long-lived charged particle producing a displaced-lepton signal at the High-Luminosity LHC is also the mediator responsible for Majorana neutrino masses—the shared-coupling condition—the Casas–Ibarra parametrization determines the lepton flavor ratio $N_e/N_\mu$ of time-delayed leptons in terms of Pontecorvo–Maki–Nakagawa–Sakata (PMNS) mixing parameters alone. Within the resulting shared-coupling class of models the ratio is fixed by oscillation data, independent of all beyond-Standard-Model mass and coupling parameters up to calculable corrections bounded by charged-lepton-flavor-violation data, yielding $N_e/N_\mu = 0.140$ for the Normal and $2.11$ for the Inverted Hierarchy—a separation of more than an order of magnitude between the two predictions. This prediction holds identically across the Scotogenic model, the Type-III seesaw, the inverse and linear seesaw, and lepton-portal dark matter, and is stable against oscillation-parameter uncertainties and detector-efficiency variations, which cancel in the ratio. A single efficiency-corrected decision criterion identifies the hierarchy, and explicit signal-yield estimates combined with an exact Poisson test show that $\mathcal{O}(25)$ displaced-lepton events suffice for a $3\sigma$ discrimination with the timing infrastructure already under construction at CMS and ATLAS—so that a positive long-lived-particle signal would simultaneously resolve the mass ordering, with no dependence on $\delta_{CP}$.
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High Energy Physics (Experiment) · Cross-listed from astro-ph.HE

A Differentiable Neural Surrogate for Photon Propagation in Neutrino Telescopes

Felix J. Yu, Berthy T. Feng, Nicholas Kamp et al. (+1 more)

Large-volume neutrino telescopes infer neutrino properties from Cherenkov light, but simulating the transport of billions of photons through highly scattering ice or water is computationally costly. We introduce candela, a differentiable SIREN neural field that learns the photon Green's function of the IceCube Neutrino Observatory, a cubic-kilometer detector embedded in Antarctic glacial ice. Given a point-like energy deposit and sensor, it predicts the expected photon yield and full arrival-time distribution at the sensor. Complete events are simulated by decomposing charged-particle energy deposits into point-like sources and superposing their predicted sensor responses. Trained on Monte-Carlo simulations, candela generates events $50$–$100\times$ faster than existing methods, with cost scaling only weakly with neutrino energy. It keeps median yields within $2\%$ of the MC expectation and timing distributions at the MC statistical floor across six photon-count decades. The model also provides end-to-end gradients with respect to event parameters and opens a path toward optimizing scattering-medium properties, which often dominate systematic uncertainties in neutrino telescopes.
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All authors Felix J. Yu, Berthy T. Feng, Nicholas Kamp, Carlos A. Argüelles

High Energy Physics (Experiment) · Cross-listed from hep-ph

Systematic study of baryon-baryon interactions in singly bottomed systems

Yuxuan Du, Yanyue Pan, Xinmei Zhu et al. (+3 more)

In this work, we systematically investigate the baryon-baryon interactions in singly bottomed dibaryon systems within the chiral quark model and search for possible bound states. By exploring the baryon-baryon interaction, we find that low-isospin channels tend to generate deeper attractive interactions and are prone to form bound states. We also find that decuplet-decuplet systems tend to show stronger attraction and support a larger number of bound states, whereas octet-octet systems generally exhibit weaker attraction and fewer bound solutions. The binding behavior of octet-decuplet systems generall lies between these two cases. Several bound states are obtained, which are $\Delta\Sigma_b^*$ with $IJ=\frac{1}{2}0$, $\frac{1}{2}1$, $\frac{1}{2}2$, $\frac{1}{2}3$, and $\frac{3}{2}3$, the $\Delta\Sigma_b$ with $IJ=\frac{1}{2}1$, $\frac{1}{2}2$, $\frac{3}{2}1$, and $\frac{3}{2}2$, the $N\Sigma_b^*$ with $IJ=\frac{1}{2}2$, the $\Sigma\Sigma_b$ with $IJ=00$, $01$, and $11$, the $\Sigma\Sigma_b^*$ with $IJ=01$ and $02$, the $\Sigma^*\Sigma_b$ with $IJ=01$ and $02$, and the $\Sigma^*\Sigma_b^*$ with $IJ=00$, $01$, $02$, $03$, and $13$. Further investigations of the corresponding scattering processes are still required to determine whether these bound-state candidates can be identified. These states deserve further experimental investigation.
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All authors Yuxuan Du, Yanyue Pan, Xinmei Zhu, Zhiyun Tan, Hongxia Huang, Jialun Ping

Thursday 3 September

High Energy Physics (Experiment) · Cross-listed from physics.data-an

Theoretical–operational modelling of complex experiments: parameter robustness and degeneracy in muon–electron conversion

Vitaly Pronskikh

Complex experiments infer theory parameters through a coupled chain of physical models and data reduction. We formulate the theoretical–operational model (TOM) as a typed factorization of this forward prediction and study how changes of preparation, phenomenon modelling, readout, backgrounds, and analysis project onto the local manifold generated by the physics parameters. For a smooth prediction and a locally identifiable weighted least-squares estimate, the resulting response map separates each model deformation into a parameter-equivalent component and a residual component that cannot be absorbed by a change of the fitted physics parameters. This gives local criteria for robustness, exact degeneracy, and partial degeneracy of parameter inference. The construction is applied to charged-lepton-flavour-violating muon–electron conversion in aluminium. A one-bin conversion-rate model exhibits an exact normalization degeneracy. In a two-template model of the elastic–inelastic spectrum, a common signal normalization is absorbed by the fitted conversion rate without changing an operator-sensitive nuclear-response ratio, whereas a relative elastic–inelastic efficiency change is exactly parameter-equivalent to a change of that ratio at first order. A numerical Run-I example based on published Mu2e spectra shows that a \(100\,\mathrm{keV}/c\) momentum-scale mismatch is only partially parameter-equivalent: its projection ratio onto the local tangent space generated by the elastic normalization \(R_0\) and the logarithmic inelastic-to-elastic response ratio \(\rho\) is \(\eta=0.331\), while most of the weighted spectral deformation remains as a residual shape. TOM thereby provides a local theoretical description of parameter robustness and degeneracy at the interface of particle/nuclear phenomenology and experimental realization.
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High Energy Physics (Experiment)

Search for the rare Higgs boson decay H $\to$ Z$\gamma$ in proton-proton collisions at $\sqrt{s}$ = 13 and 13.6 TeV

CMS Collaboration

A search is presented for the rare, loop-induced Higgs boson decay H $\to$ Z$\gamma$, where Z $\to$ $\ell^+\ell^-$ and $\ell$ = e or $\mu$. The search is performed using a sample of proton-proton (pp) collision data at the center-of-mass energies of 13 and 13.6 TeV, recorded by the CMS experiment at the LHC and corresponding to a total integrated luminosity of 200 fb$^{-1}$. The analysis design separately considers and optimizes sensitivity to Higgs boson production via gluon-gluon fusion, vector boson fusion, and associated-production processes. The signal is extracted from a simultaneous fit to the invariant mass distributions of the $\ell^+\ell^-\gamma$ system in the various production channels and event categories. The observed (expected) signal strength $\mu$, defined as the ratio of the measured product the of cross section and decay branching fraction value $\sigma$(pp $\to$ H)$\mathcal{B}$(H $\to$ Z$\gamma$) to the corresponding value predicted in the standard model, is found to be $\mu$ = 1.10$^{+0.52}_{-0.61}$ (1.00$^{+0.49}_{-0.46}$) for a Higgs boson mass of 125.38 GeV. The signal has an observed (expected) significance of 1.9 (2.3) standard deviations.
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High Energy Physics (Experiment) · Cross-listed from hep-ph

$Z$-plus-jet Production with JETHAD-DYnamis: Angular Structure, Polarization, Fixed-Order Matching

Francesco Giovanni Celiberto and Francesca Lonigro

Recent NLO analyses of inclusive Higgs production indicate that high-energy resummation corrections can reach the 10% level, highlighting the growing impact of high-energy QCD dynamics on electroweak observables from LHC to FCC energies. We extend this precision program to Drell-Yan plus jet production by deriving high-energy-resummed predictions for rapidity and transverse-momentum distributions of electroweak bosons. Fixed-order NLO accuracy is consistently combined with next-to-leading energy-logarithmic resummation (NLL/NLO). We outline a JETHAD-DYnamis-POWHEG matching strategy that retains polarization and angular correlations while enabling realistic lepton-level kinematics. This setup provides the first high-energy-resummed description of rapidity-separated electroweak-boson plus jet final states. The resulting framework offers a precision-oriented description of Drell-Yan observables for present LHC measurements and the High-Luminosity LHC, where percent-level theoretical control will become increasingly important.
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High Energy Physics (Experiment) · Cross-listed from nucl-ex

Spin-dependent azimuthal asymmetry of coherent J/$\psi$ photoproduction in hadronic PbPb collisions at $\sqrt{s_\mathrm{NN}}$ = 5.36 TeV

CMS Collaboration

We report a measurement of the azimuthal asymmetry of muons from the decay of coherently photoproduced J/$\psi$ mesons with respect to the second-order event plane in hadronic lead-lead (PbPb) collisions. The analysis is based on data collected by the CMS experiment at the LHC at a nucleon-nucleon center-of-mass energy of 5.36 TeV, corresponding to an integrated luminosity of 1.26 nb$^{-1}$. The asymmetry is quantified using the amplitude $A_{2}$ of the second-order harmonic modulation of the decay-muon azimuthal distribution. A negative $A_{2}$ = $-$0.194 $\pm$ 0.022 (stat.) $\pm$ 0.018 (syst.) is observed with a significance greater than five standard deviations for the first time. The $A_{2}$ values show no significant dependence on the J/$\psi$ meson rapidity or the degree of overlap of the colliding ions. A theoretical model in which the coherently photoproduced J/$\psi$ meson inherits the linear polarization of the incident photon is consistent with the data. When considered together with recent measurements of coherent $\rho^0$ $\to$ $\pi^+\pi^-$ photoproduction in ultraperipheral collisions, these results provide a direct observation of spin dependence in the azimuthal asymmetry of decay products from coherently photoproduced vector mesons. In addition, the observed correlation with the event plane may enable a novel approach to reaction plane determination in the future.
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High Energy Physics (Experiment) · Cross-listed from hep-ph

Quantum Graph Neural Networks for Jet Tagging on Quantum Hardware

Benjamin Jobilal, Jinghong Yang, Trevor Smith et al. (+3 more)

Jets are central to the physics programs of both current and future colliders, from precision Standard Model measurements and searches for new physics at the Large Hadron Collider to studies of nucleon structure at the future Electron-Ion Collider. Motivated by these applications, we explore quantum machine learning for jet classification and present a permutation-invariant Quantum Graph Neural Network (QGNN) applied to particle-cloud representations of jets. We apply the model to two such discrimination tasks: quark vs. gluon and up vs. down quark flavor tagging, with the latter being, to our knowledge, the first application of a quantum model to this problem. In the ideal simulation, the QGNN performs competitively against the Particle Flow Network and traditional QCD observables. We further deploy scaled-down models to IBM and IonQ quantum processing units (QPUs), where we train and evaluate them, obtaining promising results. Finally, we perform an interpretability analysis to characterize the observables learned by the quantum model, relating them to generalized angularities for the quark-gluon study and to jet charge for the flavor study.
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All authors Benjamin Jobilal, Jinghong Yang, Trevor Smith, Vincent Calvo, Zhong-Bo Kang, Shabnam Jabeen

High Energy Physics (Experiment) · Cross-listed from hep-ph

Probing $\nu$SMEFT at Belle II with displaced dilepton vertices

Patrick D. Bolton, Fabian Esser, Lukáš Gráf et al. (+3 more)

The existence of right-handed (RH) neutrinos is strongly motivated by the observation of small neutrino masses and as a means to shed light on the origin of parity violation in the Standard Model (SM). Experimental searches for the corresponding mass eigenstates, referred to as heavy neutral leptons (HNLs), have been carried out in a variety of experiments and within different HNL models. In the current work we use the SM effective field theory with added RH neutrinos, known as $\nu$SMEFT, to study GeV-scale HNL production in $e^+e^-$ collisions at the Belle~II experiment. We focus on leptonic decays of long-lived HNLs that produce a displaced vertex in the Belle~II detector. Accounting for detection efficiency and backgrounds, we estimate the sensitivity of Belle~II to the new-physics scale of four-fermion, Higgs-current, and dipole operators in $\nu$SMEFT. We find that for most operators, the search we propose probes large regions of parameter space that are not excluded by other searches.
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All authors Patrick D. Bolton, Fabian Esser, Lukáš Gráf, Juraj Klarić, Suchita Kulkarni, Abner Soffer

High Energy Physics (Experiment) · Cross-listed from hep-ph

Atmospheric neutrino up-scattering explanation of LZ 2026 excess

Sk Jeesun and Anirban Majumdar

The recent observation of an isolated nuclear recoil at $248\pm 23\pm 23$ keV energy by the LUX-ZEPLIN (LZ) experiment has motivated the community to look for a new physics explanation, as the Standard Model background estimation fails to accommodate it. Most of the existing literature hitherto considers a galactic halo dark matter with a heavier partner. In this work, we traverse the alternate route of atmospheric neutrino ($\nu$) up-scattering, thus producing a massive beyond standard model (BSM) particle $\chi$ with mass $m_\chi$. The kinematic requirement of such a scattering demands a higher energy of the incoming neutrinos than elastic scattering, explaining the absence of excess events from solar $\nu$ scattering. However, for high energy neutrinos in the tail of the atmospheric neutrino flux, the kinematic threshold no longer prevents events at low recoil energies. To avoid an excess of such events, we consider a momentum dependent operator, which suppresses the event rate at low recoil energies and allows a single event in the high recoil energy window. Such up-scattering on nuclei ($\mathcal{N}$), $\nu \mathcal{N}\to \chi \mathcal{N}$, can be naturally realized in sterile neutrino models, though we keep our analysis generic without specifying $\chi$. We identify the region of parameter space that can produce such an isolated event, assuming a pseudoscalar mediator with mass $m_\phi$ that couples to the $\nu$-$\chi$ pair with strength $y_\chi$ and to up quarks with strength $y_u$. For example, $m_\chi \simeq 1.13$~GeV, $m_\phi \simeq 494$~MeV and $\sqrt{y_\chi y_u} \simeq 0.33$ can account for the observed event while remaining allowed by other existing constraints.
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High Energy Physics (Experiment) · Cross-listed from hep-ph

Inelastic Signatures of Electroweak Dark Matter

Juri Smirnov, Spencer Griffith and John F. Beacom

Minimal dark matter extended to include a Majorana and a Dirac multiplet coupled through the Higgs — the HC-MDM model — provides a compelling and predictive framework. We show that in certain limits of this model, the mass splitting and the inelastic interaction are representation-independent, while the thermal-relic masses are representation-dependent. We then show that this model can account for the high-energy recoil event recently reported by LUX-ZEPLIN (LZ) while also respecting thermal-relic, elastic-scattering, and solar-capture constraints. Generic inelastic DM models do not connect all these tests and generic Higgsino models do not survive them.
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High Energy Physics (Experiment) · Cross-listed from physics.ins-det

Monitoring antiproton numbers with a CMOS detector in a dense-track environment

C. Regenfus, P. Adrich, I. Belosevic et al. (+42 more)

The production of antihydrogen by the GBAR experiment at AD/ELENA requires good knowledge of the number of incident keV antiprotons, which can be problematic. We have used a commercial CMOS digital camera mounted around the experimental vacuum chamber to determine antiproton numbers from ionising particles created in the annihilation process on the surface of microchannel plate detectors which are used for beam imaging. We show that the multiplicity of emerging charged particles is as expected for individual annihilations of antiprotons with nucleons at rest, taking into account the surrounding material budget. Most of those particles are in the minimal ionising regime, but can be detected with nearly 100% efficiency in the CMOS pixel detector, while due to the thin depletion layer the device is insensitive to background gammas. Thanks to the high granularity and small pixel size millions of antiproton annihilations can be reconstructed in a dense tracking environment over a large dynamic range with good resolution. From cluster length studies of non perpendicular tracks the thickness of the depletion zone and effective detection area was estimated. The cluster length also allows for a monitoring of track angles. Antiproton numbers are determined from the number of reconstructed clusters in the CMOS sensor by means of the covered solid angle relative to a calibration measurements with well known beam intensities at the most upstream location of the GBAR apparatus. Material effects on the emerging annihilation products were estimated by Monte Carlo (Geant4) calculations, while annihilation artefacts on the complex surface of a microchannel plate are cancelled out in this approach. This method minimises largely systematic uncertainties, leading to a final error of roughly 10% for the reconstruction of absolute antiproton numbers.
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All authors C. Regenfus, P. Adrich, I. Belosevic, F. Benkel, M. Chung, P. Cladé, P. Comini, P. Crivelli, P. Debu, A. Douillet, S. Geffroy, S. Guellati-Khelifa, P. Guichard, P.-A. Hervieux, L. Hilico, P. Indelicato, S. Jonsell, J.-P. Karr, B. Kim, S. Kim, E.-S. Kim, N. Kuroda, B. Lee, L. Liszkay, D. Lunney, G. Manfredi, B. Mansoulié, V. Martimort, M. Matusiak, V. Nesvizhevsky, F. Nez, K. Park, N. Paul, E. Perez, P. Pérez, C. Roumegou, J.-Y. Roussé, F. Schmidt-Kaler, K. Szymczyk, T. A. Tanaka, B. Tuchming, D.-P. van der Werf, D. Won, S. Wronka, P. Yzombard

High Energy Physics (Experiment) · Cross-listed from hep-ph

TQ4Q2.0 Fragmentation Functions for Fully Heavy Tetraquark Production

Francesco Giovanni Celiberto

We investigate the fragmentation dynamics underlying the production of fully heavy tetraquarks by means of the TQ4Q2.0 collinear FF set, covering scalar ($0^{++}$), axial-vector ($1^{+-}$), and tensor ($2^{++}$) configurations. The fragmentation inputs are determined within NRQCD factorization for the complete set of relevant partonic channels and are subsequently evolved across heavy-flavor thresholds through the HF-NRevo scheme. Perturbative uncertainties associated with fragmentation-scale variations are consistently propagated together with nonperturbative effects encoded in color-composite long-distance matrix elements. Attention is devoted to the axial-vector sector, whose fragmentation pattern makes it especially sensitive to intrinsic-charm contributions at LHC and FCC energies. TQ4Q2.0 therefore provides an uncertainty-aware framework for exploring fully heavy tetraquark production over a broad kinematic range and for connecting exotic-hadron spectroscopy with the partonic structure of the proton.
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