arXiv subjects

N. Sinha

Publications and source records attributed to N. Sinha.

15 recordsLinked to original sources

arXiv2022

Simulated Thick, Fully-Depleted CCD Exposures Analyzed with Deep Learning Techniques

Thick, Charge Coupled Devices (CCDs) have recently been explored for applied physics, such as nuclear explosion monitoring, and dark matter detection purposes. When run in fully-depleted mode, these devices are sensitive detectors for energy depositions by a variety of primary particles. In this study we are interested in applying the Deep Learning (DL) technique known as panoptic segmentation to simulated CCD images to identify, attribute and measure energy depositions from radioisotopes of interest. We simulate CCD exposures of a chosen radioxenon isotope, $^{135}$Xe, and overlay a simulated cosmic muon background appropriate for a surface-lab. We show that with this DL technique we can reproduce the beta spectrum to good accuracy, while suffering expected confusion with same-topology gammas and conversion electrons and identifying cosmic muons less than optimally.

physics.ins-det↗

arXiv2018

Long-term evolution of the heliospheric magnetic field inferred from cosmogenic $^{44}$Ti activity in meteorites

Typical reconstructions of historic heliospheric magnetic field (HMF) $B_{\rm HMF}$ are based on the analysis of the sunspot activity, geomagnetic data or on measurement of cosmogenic isotopes stored in terrestrial reservoirs like trees ($^{14}$C) and ice cores ($^{10}$Be). The various reconstructions of $B_{\rm HMF}$ are however discordant both in strength and trend. Cosmogenic isotopes, which are produced by galactic cosmic rays (GCRs) impacting on meteoroids and whose production rate is modulated by the varying HMF convected outward by the solar wind, may offer an alternative tool for the investigation of the HMF in the past centuries. In this work, we aim to evaluate the long-term evolution of $B_{\rm HMF}$ over a period covering the past twenty-two solar cycles by using measurements of the cosmogenic $^{44}$Ti activity ($τ_{1/2} = 59.2 \pm 0.6$ yr) measured in 20 meteorites which fell between 1766 and 2001. Within the given uncertainties, our result is compatible with a HMF increase from $4.87^{+0.24}_{-0.30}$ nT in 1766 to $6.83^{+0.13}_{-0.11}$ nT in 2001, thus implying an overall average increment of $1.96^{+0.43}_{-0.35}$ nT over 235 years since 1766 reflecting the modern Grand maximum. The $B_{\rm HMF}$ trend thus obtained is then compared with the most recent reconstructions of the near-Earth heliospheric magnetic field strength based on geomagnetic, sunspot number and cosmogenic isotope data.

astro-ph.SR↗

arXiv2007

Carbon Nanotube Thin Film Field Emitting Diode: Understanding the System Response Based on Multiphysics Modeling

In this paper, we model the evolution and self-assembly of randomly oriented carbon nanotubes (CNTs), grown on a metallic substrate in the form of a thin film for field emission under diode configuration. Despite high output, the current in such a thin film device often decays drastically. The present paper is focused on understanding this problem. A systematic, multiphysics based modelling approach is proposed. First, a nucleation coupled model for degradation of the CNT thin film is derived, where the CNTs are assumed to decay by fragmentation and formation of clusters. The random orientation of the CNTs and the electromechanical interaction are then modeled to explain the self-assembly. The degraded state of the CNTs and the electromechanical force are employed to update the orientation of the CNTs. Field emission current at the device scale is finally obtained by using the Fowler-Nordheim equation and integration over the computational cell surfaces on the anode side. The simulated results are in close agreement with the experimental results. Based on the developed model, numerical simulations aimed at understanding the effects of various geometric parameters and their statistical features on the device current history are reported.

cond-mat.mtrl-sci↗

arXiv2007

Modeling the Field Emission Current Fluctuation in Carbon Nanotube Thin Films

Owing to their distinct properties, carbon nanotubes (CNTs) have emerged as promising candidate for field emission devices. It has been found experimentally that the results related to the field emission performance show variability. The design of an efficient field emitting device requires the analysis of the variabilities with a systematic and multiphysics based modeling approach. In this paper, we develop a model of randomly oriented CNTs in a thin film by coupling the field emission phenomena, the electron-phonon transport and the mechanics of single isolated CNT. A computational scheme is developed by which the states of CNTs are updated in time incremental manner. The device current is calculated by using Fowler-Nordheim equation for field emission to study the performance at the device scale.

cond-mat.mtrl-sci↗

arXiv2005

The Discovery Potential of a Super B Factory

The Proceedings of the 2003 SLAC Workshops on flavor physics with a high luminosity asymmetric e+e- collider. The sensitivity of flavor physics to physics beyond the Standard Model is addressed in detail, in the context of the improvement of experimental measurements and theoretical calculations.

hep-ph↗

arXiv2004

Probing New Physics via an Angular Analysis of B --> V1 V2 decays

We show that an angular analysis of B --> V1 V2 decays yields numerous tests for new physics in the decay amplitudes. Unlike direct CP asymmetries, many of these new-physics observables are nonzero even if the strong phase differences vanish. For certain observables, neither time-dependent measurements nor tagging is necessary. Should a signal for new physics be found, one can place a lower limit on the size of the new-physics parameters, as well as on their effect on the measurement of the phase of B0--Bbar0 mixing.

hep-ph↗

arXiv2002

New Physics in B -> J/Psi K^*

Direct CP violation in B -> J/Psi K is a clean test for new physics. However, the direct CP asymmetry will vanish if the new-physics amplitude has the same strong phase as the standard-model amplitude. We show that this type of new physics can still be detected via an angular analysis of the sister decay mode B -> J/Psi K^*. Time-dependent measurements and tagging are not necessary. Should new physics be found, this angular analysis can be used to obtain information about the size of the new-physics parameters.

hep-ph↗

arXiv2001

Extracting Weak Phase Information from B -> V_1 V_2 Decays

We describe a new method for extracting weak, CP-violating phase information, with no hadronic uncertainties, from an angular analysis of B -> V_1 V_2 decays, where V_1 and V_2 are vector mesons. The quantity $\sin^2 (2 ϕ_1 + ϕ_3)$ (ϕ_1=βand ϕ_3=γ) can be cleanly obtained from the study of decays such as B_d^0(t) -> D^{*\pm} ρ^\mp, D^{*\pm} a_1^{\mp}, D^{*0} K^{*0}, etc. Similarly, one can use B_s^0(t) -> D_s^{*\pm} K^{*\mp} or even B\pm -> D^{*0}K^*\pm to extract $\sin^2 ϕ_3$. There are no penguin contributions to these decays. It is possible that $\sin^2 (2ϕ_1 + ϕ_3)$ will be the second function of CP phases, after $\sin 2ϕ_1$, to be measured at B-factories.

hep-ph↗

arXiv2001

Searching for New Physics via CP Violation in B -> pi pi

We show how B -> pi pi decays can be used to search for new physics in the b -> d flavour-changing neutral current. One needs one piece of theoretical input, which we take to be a prediction for P/T, the ratio of the penguin and tree amplitudes in Bd -> pi+ pi-. If present, new physics can be detected over most of the parameter space. If α(ϕ_2) can be obtained independently, measurements of B+ -> pi+ pi0 and Bd/Bd(bar) -> pi0 pi0 are not even needed.

hep-ph↗

arXiv2000

Searching for New Physics via CP Violation in B -> pi pi

It is well known that one can use B -> pi pi decays to probe the CP-violating phase α. In this paper we show that these same decays can be used to search for new physics. This is done by comparing two weak phases which are equal in the standard model: the phase of the t-quark contribution to the b -> d penguin amplitude, and the phase of Bd-Bd(bar) mixing. In order to make such a comparison, we require one piece of theoretical input, which we take to be a prediction for |P/T|, the relative size of the penguin and tree contributions to Bd -> pi^+ pi^-. If independent knowledge of αis available, the decay Bd(t) -> pi^+ pi^- alone can be used to search for new physics. If a full isospin analysis can be done, then new physics can be found solely through measurements of B -> pi pi decays. The most promising scenario occurs when the isospin analysis can be combined with independent knowledge of α. In all cases, the prospects for detecting new physics in B -> pi pi decays can be greatly improved with the help of additional measurements which will remove discrete ambiguities.

hep-ph↗

arXiv2000

Angular Distribution and CP Asymmetries in the Decays B->K^-pi^+e^-e^+ and B->pi^-pi^+e^-e^+

The short-distance Hamiltonian describing b->s(d)e^-e^+ in the standard model is used to obtain the decay spectrum of \bar{B}->K^-pi^+e^-e^+ and \bar{B}->pi^-pi^+e^-e^+, assuming the Kpi and pipi systems to be the decay products of K^* and rho respectively. Specific features calculated are (i) angular distribution of K^- (or pi^-) in the K^-pi^+ (or pi^-pi^+) centre-of-mass (c.m.) frame; (ii) angular distribution of e^- in the e^-e^+ c.m. frame; and (iii) the correlation between the meson and lepton planes. We also derive CP-violating observables obtained by combining the above decays with the conjugate processes B->K^+pi^-e^-e^+ and B->pi^-pi^+e^-e^+.

hep-ph↗

arXiv2000

Is it possible to Measure the Weak Phase of a Penguin Diagram?

The $b\to d$ penguin amplitude receives contributions from internal $u$, $c$ and $t$-quarks. We show that it is impossible to measure the weak phase of any of these penguin contributions without theoretical input. However, a single assumption involving the hadronic parameters makes it possible to obtain the weak phase and test for the presence of new physics in the $b\to d$ flavour-changing neutral current.

hep-ph↗

arXiv1999

Can One Measure the Weak Phase of a Penguin Diagram?

The b -> d penguin amplitude receives contributions from internal u, c and t-quarks. We show that it is impossible to measure the weak phase of any of these penguin contributions without theoretical input. However, it is possible to obtain the weak phase if one makes a single assumption involving the hadronic parameters. With such an assumption, one can test for the presence of new physics in the b -> d flavour-changing neutral current by comparing the weak phase of B_d^0-{\bar B}_d^0 mixing with that of the t-quark contribution to the b -> d penguin.

hep-ph↗

arXiv1995

Probing Anomalous Triple Boson Vertices at Future $e^+e^-$ Colliders

We explore the detection potential of the four lepton production processes $e^{+}e^{-} \rightarrow l^{+} νl^{\prime -}\overlineν$ for anomalous contributions to the triple boson vertices at proposed future high energy colliders with center-of-mass energies of 500 GeV and 1 TeV. The predicted bounds are of the order of a few percent for the $CP$-even couplings $κ_{V}$ (V=$γ$,Z) at the higher energy; we show that these limits can be improved by as much as a factor of two through suitable phase space cuts. A polarized beam facility, with its ability to access helicity information, could provide constraints on the vertices significantly tighter than those achievable from an analysis of total cross-section alone. The asymmetries in experimental observables produced by an explicitly $CP$ violating triple vertex contribution are seen to be below the expected level of statistical precision of approximately $1.5 \%$; asymmetries in the individual contributing helicity amplitudes might however be detectable.

hep-ph↗

arXiv1993

Extracting W Boson Couplings from the $e^{+}e^{-}$ Production of Four Leptons

We consider the processes $e^{+}e^{-}\rightarrow \ell^{+} \ell^{\prime -}ν\barν^{\prime}$, including all possible charged lepton combinations, with regard to measuring parameters characterizing the $W$ boson. We calculate at what level these processes can be used to measure anamolous triple-boson vertice coupling parameters for the cases of $e^{+}e^{-}$ colliders at 500 $GeV$ and 1 $TeV$ center of mass energies.

hep-ph↗