arXiv subjects

V. Sharma

Publications and source records attributed to V. Sharma.

At least 19 recordsLinked to original sources

arXiv2026

Constraining Axion-Like-Particles with germanium detector at the Kuo-Sheng Reactor Neutrino Laboratory

We present results of a search for Axion-Like Particles (ALPs) produced $via$ Primakoff and Compton-like scattering channels, using data acquired with TEXONO experiment at the Kuo-Sheng Nuclear Power Station. The analysis is based on 278.91 days of reactor-ON and 43.60 days of reactor-OFF data. These datasets were collected using a 1.06 kg high-purity germanium detector located 28 m from a 2.9 GW reactor core. No significant excess is observed in the residual spectrum from the reactor-ON and reactor-OFF data subtraction. Using data acquired with low-background germanium detectors, upper limits on both the ALP-photon ($g_{a\gamma\gamma}$) and ALP-electron ($g_{aee}$) couplings are derived for ALP masses ranging from 1 eV to 3 MeV at 90\% confidence level. Since both $g_{a\gamma\gamma}$ and $g_{aee}$ couplings contribute to ALP production and detection, a combined analysis is performed by treating both channels as active parameters.

hep-ex↗

arXiv2026

Studies of Neutrino-Nucleus Elastic Scattering with Point-Contact Germanium Detectors at the Kuo-Sheng Reactor Neutrino Laboratory

The low energy and intense flux of electron anti-neutrinos from nuclear reactors provide the perfect stage to study elastic neutrino-nucleus scattering ($\nu A_{el}$) in the fully coherent regime. We report results from the TEXONO experiment using electro-cooled $p$-type point-contact Germanium detectors with masses of 523~g and 1434~g at the Kuo-Sheng Reactor Neutrino Laboratory. We report improved constraints on the $\nu A_{el}$ cross section with a combined exposure of 404(813.7)~kg-days of Reactor ON(OFF) data at an electron-equivalent threshold of 200~eV$_{ee}$. The Lindhard model, in which the quenching factor is parameterized by a single parameter k, is adopted to describe the suppression of ionization yield. At the benchmark value of k=0.162, a limit of $\rho<$2.0 at 90\% confidence level (CL) is derived, where $\rho$ represents the ratio of the observed to the predicted Standard Model cross section. Moreover the region k$>$0.205 is excluded at 90\% CL using the SM-predicted $\nu A_{el}$ rate. A bound on the neutrino magnetic moment from $\nu A_{el}$ at $\mu_{\nu} {<} 5.9 \times 10^{-10}~\mu_B$ at 90\% CL is also derived.

hep-ex↗

arXiv2026

Vibrational sensing at mK temperatures in dry dilution refrigerators using commercial accelerometers for diverse fundamental physics applications

This article presents an evaluation of off-the-shelf commercial accelerometers at the mixing chamber stage of a cryogen-free dilution refrigerator at temperatures down to 8 mK. In addition, we present results of radioassay of accelerometers using a high purity germanium detector counting setup. Cryogen-free dilution refrigerators using pulse-tube cryocoolers (PTs) -- due to recent advances in their cooling capacity, long-term stability, and operational costs -- have become ubiquitous tools in a wide range of fields ranging from experimental particle physics to quantum information sciences. However, vibrations induced by PTs can negatively impact the experimental payload in these applications. This work demonstrates that commercially available accelerometers can not only measure vibrations at millikelvin cryogenic temperatures but also pave the way for continuous, in situ, real-time vibration monitoring of dry dilution refrigerators. This monitoring capability facilitates applications such as real-time denoising for vibration-sensitive experiments, thereby enabling ongoing noise assessment and mitigation.

physics.ins-det↗

arXiv2026

Cyclotron Radiation Signal Characterization in Resonant Cavities for the Project 8 Neutrino Mass Experiment

Many experimental methods in physics require understanding radiation from single particles into non-trivial electromagnetic mode structures. Such characterization is critical for Cyclotron Radiation Emission Spectroscopy (CRES), an advancing new measurement technique that has the potential to greatly benefit fundamental physics measurements. In CRES, charged particles emit cyclotron radiation at frequencies that provide their energy measurement. As a notable example, the Project 8 experiment aims to kinematically infer the neutrino mass by measuring the energies of electrons emitted in tritium beta decay using CRES. In near-term realizations of Project 8, resonant cylindrical cavities will be used for CRES readout, in a configuration with a magnetic field oriented along the symmetry axis, and electrons following helical cyclotron trajectories confined to the cavity interior. The physics of electromagnetic radiation in these environments is complicated, since it involves both the motion of the emitting particle and the mode structure imposed by the cavity. In this work, we derive and validate an analytic model for how an oscillating, trapped electron radiates into cavity modes, and the power and frequency content of the radiation that can be read out from these events. These results can be used to guide the design of cavities for future CRES and other experiments.

physics.ins-det↗

arXiv2025

Antenna Arrays for CRES-based Neutrino Mass Measurement

CRES is a technique for precision measurements of kinetic energies of charged particles, pioneered by the Project 8 experiment to measure the neutrino mass using the tritium endpoint method. It was recently employed for the first time to measure the molecular tritium spectrum and place a limit on the neutrino mass using a cm$^3$-scale detector. Future direct neutrino mass experiments are developing the technique to overcome the systematic and statistical limitations of current detectors. This paper describes one such approach, namely the use of antenna arrays for CRES in free space. Phenomenology, detector design, simulation, and performance estimates are discussed, culminating with an example design with a projected sensitivity of $m_{\beta} < 0.04 \ \mathrm{eV}/c^2$. Prototype antenna array measurements are also shown for a demonstrator-scale setup as a benchmark for the simulation. By consolidating these results, this paper serves as a comprehensive reference for the development and performance of antenna arrays for CRES.

physics.ins-det↗

arXiv2025

Half-life and precision shape measurement of 2{\nu}{\beta}{\beta} decay of $^{130}$Te

We present a new measurement of the 2nbb half-life of 130Te (T1/2) using the first complete model of the CUORE data, based on 1038 kg yr of collected exposure. Thanks to optimized data selection, we achieve a factor of two improvement in precision, obtaining T1/2 = (9.32 +0.05 -0.04 (stat.) +0.07 -0.07 (syst.)) x10^20 yr. The signal-to-background ratio is increased by 70% compared to our previous results, enabling the first application of the improved 2nbb formalism to 130Te. Within this framework, we determine a credibility interval for the effective axial coupling in the nuclear medium as a function of nuclear matrix elements. We also extract values for the higher-order nuclear matrix element ratios: second-to-first and third-to-first. The second-to-first ratio agrees with nuclear model predictions, while the third-to-first ratio deviates from theoretical expectations. These findings provide essential tests of nuclear models and key inputs for future 0nbb searches.

nucl-ex↗

arXiv2025

Constraints on New Physics with Light Mediators and Generalized Neutrino Interactions via Coherent Elastic Neutrino Nucleus Scattering

We investigate new physics effects on coherent elastic neutrino nucleus scattering within the framework of nonstandard interactions and generalized neutrino interactions. Additionally, we examine the possibility of light mediators from a simplified model that includes all possible Lorentz-invariant interactions of vector, axialvector, scalar, pseudoscalar, and tensor types. Constraints and allowed regions at the $90\%$ CL for masses and couplings in each new physics scenario have been obtained through the analysis of TEXONO data, which includes two datasets from a high-purity $n$-type point contact germanium detector in 2016 and an advanced $p$-type point contact Ge detector in 2025. The results are presented in comparison with other reactor and accelerator-based neutrino experiments for complementarity.

hep-ex↗

arXiv2025

Cooper-Pair Localization in the Magnetic Dynamics of a Cuprate Ladder

We investigate the spin dynamics of the cuprate ladder Sr$_{2.5}$Ca$_{11.5}$Cu$_{24}$O$_{41}$ to elucidate the behavior of its intrinsically doped holes. Combining high-resolution neutron spectroscopy and density matrix renormalization group calculations enables a comprehensive analysis of the collective magnetic dynamics. We find a general absence of magnetic signatures from unpaired charges, indicating holes within the system form strongly bound localized Cooper pairs. A one-band Hubbard model fails to match the spectral features but a straightforward extension to a large attractive nearest-neighbor interaction quantitatively explains our results. Our finding shows the significance of additional interactions beyond the long-predicted quantum spin pairing in the ($d$-wave) charge pairing process. Considering the parallels between ladders and two-dimensional cuprates, these results are potentially relevant for square lattices as well.

cond-mat.str-el↗

arXiv2024

Extremely luminous optical afterglow of an energetic gamma-ray burst GRB 230204B

Robotic telescope networks play an important role in capturing early and bright optical afterglows, providing critical insights into the energetics and emission mechanisms of GRBs. In this study, we analyze GRB 230204B, an exceptionally energetic and multi-pulsed long GRB, detected by the Fermi GBM and MAXI detectors, with an isotropic equivalent gamma-ray energy exceeding 10$^{54}$ erg. Time-resolved spectral analysis reveals a transition in the prompt emission from hard (sub-photospheric dominated) spectra during early pulses to softer (synchrotron radiation dominated) spectra in later pulses, indicative of a hybrid jet composition. We report the discovery and characterization of the optical afterglow using the MASTER and BOOTES robotic telescope networks, which enabled rapid follow-up observations starting at $\sim$1.3 ks post-burst. The optical luminosity at this time was exceptionally high, surpassing that of many other optically bright GRBs, such as GRB 990123, GRB 080319B, etc. This places the burst among the most luminous optical GRBs observed to date. Long-term radio observations extending to 335 days post-burst were conducted with the ATCA. Multi-wavelength modeling was conducted using an external ISM forward-shock top-hat jet model with \sw{afterglowpy}. The results reveal a narrow and highly collimated jet with a circumburst density of $n_{0} \sim$ 28.12 cm$^{-3}$, kinetic energy $E_{\rm K} \sim$ 4.18 $\times 10^{55}$ erg, and a relatively low value of $\epsilon_{B}$ = 2.14 $\times 10^{-6}$, indicating shock-compression of magnetic field in the surrounding interstellar medium. We constrained a low radiative efficiency of $\sim$ 4.3 \%. This study highlights the indispensable contribution of robotic networks to early afterglow observations and advances our understanding of GRB 230204B unique characteristics and underlying jet physics.

astro-ph.HE↗

arXiv2024

Dark Matter Annual Modulation Analysis with Combined Nuclear and Electron Recoil Channels

After decades of experimental efforts, the DAMA/LIBRA(DL) annual modulation (AM) analysis on the $\chi N$ (WIMP Dark Matter interactions on nucleus) channel remains the only one which can be interpreted as positive signatures. This has been refuted by numerous time-integrated (TI) and AM analysis. It has been shown that $\chi e$ (WIMP interactions with electrons) alone is not compatible with the DL AM data. We expand the investigations by performing an AM analysis with the addition of $\chi e$ long-range and short-range interactions to $\chi N$, derived using the Frozen Core Approximation method. Two scenarios are considered, where the $\chi N$ and $\chi e$ processes are due to a single $\chi$ ($\Gamma^{1 \chi}_{tot}$) or two different $\chi$'s ($\Gamma^{2 \chi}_{tot}$). The combined fits with $\chi N$ and $\chi e$ provide stronger significance to the DL AM data which are compatible with the presence of additional physical effects beyond $\chi N$ alone. This is the first analysis which explores how $\chi e$ AM can play a role in DL AM. The revised allowed regions as well as the exclusion contours from the other null AM experiments are presented. All DL AM allowed parameter spaces in $\chi N$ and $\chi e$ channels under both $\Gamma^{1 \chi}_{tot}$ and $\Gamma^{2 \chi}_{tot}$ are excluded at the 90\% confidence level by the combined null AM results. It can be projected that DL-allowed parameter spaces from generic models with interactions induced by two-WIMPs are ruled out.

hep-ex↗

arXiv2024

New Limits on Coherent Neutrino Nucleus Elastic Scattering Cross Section at the Kuo-Sheng Reactor Neutrino Laboratory

Neutrino nucleus elastic scattering ({\nu}Ael) with reactor neutrinos is an interaction under full quantum-mechanical coherence. It has not yet been experimentally observed. We present new results on the studies of {\nu}Ael cross section with an electro-cooled p-type point-contact germanium detector at the Kuo-Sheng Reactor Neutrino laboratory. A total of (242)357 kg-days of Reactor ON(OFF) data at a detector threshold of 200 eVee in electron equivalent unit are analyzed. The Lindhard model parametrized by a single variable k which characterizes the quenching function was used. Limits at 90% confidence level are derived on the ratio {\rho} relative to standard model (SM) cross section of {\rho}<4.7 at the predicted value of k=0.162, while k<0.285 at the SM-value of {\rho}=1. Prospects on future positive measurements are discussed.

nucl-ex↗

arXiv2024

A detailed time-resolved and energy-resolved spectro-polarimetric study of bright GRBs detected by AstroSat CZTI in its first year of operation

The radiation mechanism underlying the prompt emission remains unresolved and can be resolved using a systematic and uniform time-resolved spectro-polarimetric study. In this paper, we investigated the spectral, temporal, and polarimetric characteristics of five bright GRBs using archival data from AstroSat CZTI, Swift BAT, and Fermi GBM. These bright GRBs were detected by CZTI in its first year of operation, and their average polarization characteristics have been published in Chattopadhyay et al. (2022). In the present work, we examined the time-resolved (in 100-600 keV) and energy-resolved polarization measurements of these GRBs with an improved polarimetric technique such as increasing the effective area and bandwidth (by using data from low-gain pixels), using an improved event selection logic to reduce noise in the double events and extend the spectral bandwidth. In addition, we also separately carried out detailed time-resolved spectral analyses of these GRBs using empirical and physical synchrotron models. By these improved time-resolved and energy-resolved spectral and polarimetric studies (not fully coupled spectro-polarimetric fitting), we could pin down the elusive prompt emission mechanism of these GRBs. Our spectro-polarimetric analysis reveals that GRB 160623A, GRB 160703A, and GRB 160821A have Poynting flux-dominated jets. On the other hand, GRB 160325A and GRB 160802A have baryonic-dominated jets with mild magnetization. Furthermore, we observe a rapid change in polarization angle by $\sim$ 90 degrees within the main pulse of very bright GRB 160821A, consistent with our previous results. Our study suggests that the jet composition of GRBs may exhibit a wide range of magnetization, which can be revealed by utilizing spectro-polarimetric investigations of the bright GRBs.

astro-ph.HE↗

arXiv2024

Observation of sequential three-body dissociation of camphor molecule -- a native frame approach

The three-body dissociation dynamics of the dicationic camphor molecule (C$_{10}$H$_{16}$O$^{2+}$) resulting from Auger decay are investigated using soft X-ray synchrotron radiation. A photoelectron-photoion-photoion coincidence (PEPIPICO) method, a combination of a velocity map imaging (VMI) spectrometer and a time-of-flight (ToF) spectrometer is employed to measure the 3D momenta of ions detected in coincidence. The ion mass spectra and the ion-ion coincidence map at photon energies of 287.9 eV (below the C 1s ionization potential) and 292.4 eV (above the C 1s ionization potential for skeletal carbon) reveal that fragmentation depends on the final dicationic state rather than the initial excitation. Using the native frame method, three new fragmentation channels are discussed; (1) CH$_2$CO$^+$ + C$_7$H$_{11}^+$ + CH$_3$, (2) CH$_3^+$ + C$_7$H$_{11}^+$ + CH$_2$CO, and (3) C$_2$H$_5^+$ + C$_6$H$_9^+$ + CH$_2$CO. The dominating nature of sequential decay with deferred charge separation is clearly evidenced in all three channels. The results are discussed based on the experimental angular distributions and momenta distributions, corroborated by geometry optimization of the ground, monocationic, and dicationic camphor molecule.

physics.chem-ph↗

arXiv2024

Coherent Acoustic Control of Defect Orbital States in the Strong-Driving Limit

We use a bulk acoustic wave resonator to demonstrate coherent control of the excited orbital states in a diamond nitrogen-vacancy (NV) center at cryogenic temperature. Coherent quantum control is an essential tool for understanding and mitigating decoherence. Moreover, characterizing and controlling orbital states is a central challenge for quantum networking, where optical coherence is tied to orbital coherence. We study resonant multi-phonon orbital Rabi oscillations in both the frequency and time domain, extracting the strength of the orbital-phonon interactions and the coherence of the acoustically driven orbital states. We reach the strong-driving limit, where the physics is dominated by the coupling induced by the acoustic waves. We find agreement between our measurements, quantum master equation simulations, and a Landau-Zener transition model in the strong-driving limit. Using perturbation theory, we derive an expression for the orbital Rabi frequency versus acoustic drive strength that is non-perturbative in the drive strength and agrees well with our measurements for all acoustic powers. Motivated by continuous wave spin resonance-based decoherence protection schemes, we model the orbital decoherence and find good agreement between our model and our measured few-to-several nanoseconds orbital decoherence times. We discuss the outlook for orbital decoherence protection.

quant-ph↗

arXiv2024

Heavy Hexaquarks in the Flux Tube Model

Hexaquarks are one of the currently emerging topics in both experimental and theoretical high energy physics. Hexaquarks have been examined in relation to particle physics, however, there are still some research and theoretical conjectures surrounding their relationship to dark matter. Due to some experimental discoveries, it has attracted much interest and also resulted in new theoretical models to study the properties of these states. In the present work, Regge trajectories of some hexaquark states are compared with tetraquark and pentaquark states. The study is mainly concentrated on fully heavy hexaquark states. The mass spectra of these hexaquark states have also been investigated and the results are compared with other theoretical works. Our findings agree well with those of other researchers.

hep-ph↗

arXiv2023

Projections of Discovery Potentials from Expected Background

Background channels with their expected strength and uncertainty levels are usually known in searches of novel phenomena prior to the experiments are conducted at their design stage. We quantitatively study the projected sensitivities in terms of discovery potentials. These are essential for the optimizations of the experimental specifications as well as of the cost-effectiveness in various investment. Sensitivities in counting analysis are derived with complete Poisson statistics and its continuous approximation, and are compared with those using maximum likelihood analysis in which additional measurables are included as signatures. The roles and effects due to uncertainties in the background estimates are studied. Two expected features to establish positive effects are verified and quantified: (i) In counting-only experiments, the required signal strength can be derived with complete Poisson analysis, and the continuous approximation would underestimate the results. (ii) Incorporating continuous variables as additional constraints would reduce the required signal strength relative to that of counting-only analysis. The formulations are applied to the case on the experimental searches of neutrinoless double beta decay in which both ambient and two-neutrino background are considered.

hep-ex↗

arXiv2022

Azimuthal structures and turbulent transport in Penning discharge

Azimuthal structures in cylindrical Penning discharge are studied with 2D3V radial-azimuthal PIC/MCC model with the axial magnetic field. The discharge is self-consistently supported by ionization due to the axial injection of electrons. It is shown that the steady-state discharge can be supported in two different regimes with different type of observed azimuthal structures. The transition between the regimes is controlled by the mechanism of the energy input to the discharge. In the first regime (low energy of the injected electrons), with the pronounced $m=1$ spoke activity, the power input is dominated by the energy absorption due to the radial current and self-consistent electric field. In the other regime (higher energy of the injected electrons), with prevalent small scale $m>1$ spiral structures, and the lower values of the anomalous transport, the total energy deposited to the discharge is lower and is mostly due to the direct input of the kinetic energy from the axial electron beam. We show that the large (m=1) spoke and small scale structures occur as a result of Simon-Hoh and lower hybrid instabilities driven by the electric field, density gradient, and collisions. We show that the spoke frequency follows the equilibrium ion rotation frequency.

physics.plasm-ph↗

arXiv2022

Constraints on Sub-GeV Dark Matter--Electron Scattering from the CDEX-10 Experiment

We present improved germanium-based constraints on sub-GeV dark matter via dark matter--electron ($\chi$-$e$) scattering using the 205.4 kg$\cdot$day dataset from the CDEX-10 experiment. Using a novel calculation technique, we attain predicted $\chi$-$e$ scattering spectra observable in high-purity germanium detectors. In the heavy mediator scenario, our results achieve 3 orders of magnitude of improvement for $m_{\chi}$ larger than 80 MeV/c$^2$ compared to previous germanium-based $\chi$-$e$ results. We also present the most stringent $\chi$-$e$ cross-section limit to date among experiments using solid-state detectors for $m_{\chi}$ larger than 90 MeV/c$^2$ with heavy mediators and $m_{\chi}$ larger than 100 MeV/c$^2$ with electric dipole coupling. The result proves the feasibility and demonstrates the vast potential of a new $\chi$-$e$ detection method with high-purity germanium detectors in ultralow radioactive background.

hep-ex↗