Publications

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Measurement of low-energy Compton and neutron scattering in Si CCDs for dark matter searches

Radomir Smida for the DAMIC-M Collaboration

SciPost Phys. Proc. 12, 015 (2023) · published 3 July 2023 | · pdf

For optimal sensitivity to low-mass dark matter candidates experiments like DAMIC-M employ skipper charged-coupled devices (CCDs) with detection threshold of just a few ionization charges. Ionization signals from small-angle Compton scatters of environmental $\gamma$-rays, an important component of the background in dark matter searches, must thus be characterized down to $O$(10 eV) energy. Using a $^{241}$Am $\gamma$-ray source, we report a precise measurement of scattering on Si atomic shell electrons in a skipper CCD with single-electron resolution. Notable differences are observed between data and theoretical expectations in the L-shell energy region ($<$150 eV). We also present preliminary data from a skipper CCD exposed to low-energy neutrons ($<$24 keV) from a $^{124}$Sb$^9$Be photoneutron source, demonstrating a measurement of the nuclear recoil ionization efficiency in Si down to few ionization charges.
The low-energy spectrum in DAMIC at SNOLAB

Alvaro E. Chavarria

SciPost Phys. Proc. 12, 011 (2023) · published 3 July 2023 | · pdf

The DAMIC experiment employs large-area, thick charge-coupled devices (CCDs) to search for the interactions of low-mass dark matter particles in the galactic halo with silicon atoms in the CCD target. From 2017 to 2019, DAMIC collected data with a seven-CCD array (40-gram target) installed in the SNOLAB underground laboratory. We report dark-matter search results, including a conspicuous excess of events above the background model below 200$V_{ee}$, whose origin remains unknown. We present details of the published spectral analysis, and update on the deployment of skipper CCDs to perform a more precise measurement by early 2023.
T-odd quark-gluon-quark correlation function in the light-front quark-diquark model

Shubham Sharma, Narinder Kumar, Harleen Dahiya

SciPost Phys. Proc. 8, 170 (2022) · published 14 July 2022 | · pdf

We have scrutinized the transverse momentum dependent quark-gluon-quark correlation function. We have utilized the light-front quark-diquark model to study the time-reversal-odd interaction-dependent twist-3 gluon distributions which we have obtained from the disintegration of the transverse momentum dependent quark-gluon-quark correlator. Specifically, we have studied the behavior of $\tilde{e}_{L}$ and $\tilde{e}_{T}$ while considering our diquark to be an axial-vector.
Studies of $b$-hadrons and quarkonia at LHCb

Zhiyu Xiang

SciPost Phys. Proc. 8, 092 (2022) · published 13 July 2022 | · pdf

LHCb has productive studies of quarkonia and $b$-hadrons which provide essential inputs to study quantum chromodynamics (QCD). In this proceeding, seven recent results are reported: the observation of a new excited $\Xi_b^0$ resonance in $\Xi_b^- \pi^+$ final states, the new excited $B_s^0$ state is observed in $B^+ K^-$ mass spectrum, the first observation of suppressed semileptonic $B_s^0 \rightarrow K^- \mu^+ \nu_{\mu}$ decay, the first observation of the decay $B^0 \rightarrow D^0 \bar{D}^0 K^+ \pi^-$, the first observation of the Cabibbo-suppressed decay $\Lambda_b^0 \rightarrow \chi_{c1} p \pi^-$, the first observation of $\Lambda_b^0 \rightarrow \Lambda_c^+ K^+ K^- \pi^-$ decay, and end this report with the first search for the doubly heavy baryon $\Omega_{bc}^{0}$ and a search for $\Xi_{bc}^0$ baryon.
Dark matter searches and energy accumulation and release in materials

Sergey Pereverzev

SciPost Phys. Proc. 12, 009 (2023) · published 3 July 2023 | · pdf

Efforts to identify dark matter by detecting nuclear recoils produced by dark matter particles reveal low-energy backgrounds of unknown origin in different types of detectors. In many cases, energy accumulation and delayed burst-like releases of stored energy could provide an explanation. These dynamics follow Prigogine's ideas on systems with energy flow and the general Self-Organized Criticality scenario. We compare these models with properties of excess backgrounds in cryogenic solid-state detectors, relaxation processes in glasses and crystals, our observations of delayed luminescence in NaI(Tl), and make predictions for more phenomena present in these systems and in superconducting photon detectors and qubits. Experiments to create accurate phenomenological models are needed.
Ionization efficiency at sub-keV energies for crystals and noble liquids

Youssef Sarkis, Alexis A. Aguilar-Arevalo, Juan Carlos D'Olivo

SciPost Phys. Proc. 12, 008 (2023) · published 3 July 2023 | · pdf

We study the ionization and light yields produced by nuclear recoils at low energies in pure crystals and noble liquids in the context of Lindhard's integral equation, incorporating the effects of binding energy, improved modeling of the electronic stopping, and electronic straggling. We consider three different models for the electronic stopping power that incorporate Coulomb repulsion effects at low energies, and Bohr electronic stripping for high energies. Finally, we discuss possible new effects near threshold.
New $\tau$-based evaluation of the hadronic vacuum polarization contribution to the muon anomalous magnetic moment

Jesús Alejandro Miranda Hernández, Pablo Roig Garcés

SciPost Phys. Proc. 16, 032 (2025) · published 15 July 2025 | · pdf

We revisit the radiative corrections to the $\tau^-\to\pi^-\pi^0\nu_\tau(\gamma)$ decays using Resonance Chiral Theory for the structure-dependent part. This channel is the most important one to understand the hadronic vacuum polarization piece of the muon g-2, which dominates the uncertainty of its data-driven prediction in the Standard Model. Using our results, the discrepancy between theory and experiment for this observable is reduced to $\sim2.2\sigma$.
Development of the ATLAS Liquid Argon Calorimeter Readout Electronics for the HL-LHC

Mathis Kolb

SciPost Phys. Proc. 8, 158 (2022) · published 14 July 2022 | · pdf

The full ATLAS Liquid Argon Calorimeter electronic readout chain will be upgraded for the high-luminosity LHC. The upgrade is designed to withstand the expected radiation level and to be compatible with the Phase-I Digital Trigger System which is being installed right now. Analogue electronics shape and amplify the calorimeter signals before they are digitized with 16 bit dynamic range on two gain scales. The on-detector system samples the calorimeter cell signals at 40 MHz and sends them to the off-detector electronics which apply digital processing based on FPGAs. Design studies and tests of prototypes of the upgraded components are present
Towards DIS at N4LO

Avanish Basdew-Sharma

SciPost Phys. Proc. 8, 153 (2022) · published 14 July 2022 | · pdf

We will report on an ongoing effort towards calculating the N4LO perturbative QCD corrections to the DIS total inclusive cross-section. We are developing a method based on differential equations and series expansion in the inverse Bjorken parameter. As a byproduct our calculation should also deliver analytic or at least precise numerical approximations for the four-loop splitting functions.
Search for lepton-flavour-violating decays of the $Z$ boson into a $\tau$-lepton and a light lepton with the ATLAS detector

Wing Sheung Chan on behalf of the ATLAS collaboration

SciPost Phys. Proc. 1, 048 (2019) · published 22 February 2019 | · pdf

Lepton flavour violation in the charged lepton sector is an unambiguous signal of physics beyond the Standard Model. Searches for lepton flavour violation in decays of the $Z$ boson with the ATLAS detector is reported, focusing on decays into an electron or muon and a hadronically decaying $\tau$-lepton, using $pp$ collisions data with a centre-of-mass energy of 13 TeV. Upper limits on the branching ratios of lepton-flavor-violating decays are set at the 95\% confidence level: $\mathcal{B}(Z\to e\tau) < 5.8\times10^{-5}$ and $\mathcal{B}(Z\to \mu\tau) < 2.4\times10^{-5}$. When combined with a previous ATLAS result based on $pp$ collisions data with a centre-of-mass energy of 8 TeV, an upper limit of $\mathcal{B}(Z\to \mu\tau) < 1.3\times10^{-5}$ is obtained.

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