arXiv subjects

M. K. Singh

Publications and source records attributed to M. K. Singh.

At least 55 records · Page 3Linked to original sources

arXiv2018

Limits on light WIMPs with a 1 kg-scale germanium detector at 160 eVee physics threshold at the China Jinping Underground Laboratory

We report results of a search for light weakly interacting massive particle (WIMP) dark matter from the CDEX-1 experiment at the China Jinping Underground Laboratory (CJPL). Constraints on WIMP-nucleon spin-independent (SI) and spin-dependent (SD) couplings are derived with a physics threshold of 160 eVee, from an exposure of 737.1 kg-days. The SI and SD limits extend the lower reach of light WIMPs to 2 GeV and improve over our earlier bounds at WIMP mass less than 6 GeV.

hep-ex↗

arXiv2018

Limits on Light Weakly Interacting Massive Particles from the First 102.8 kg ${\times}$ day Data of the CDEX-10 Experiment

We report the first results of a light weakly interacting massive particles (WIMPs) search from the CDEX-10 experiment with a 10 kg germanium detector array immersed in liquid nitrogen at the China Jinping Underground Laboratory with a physics data size of 102.8 kg day. At an analysis threshold of 160 eVee, improved limits of 8 $\times 10^{-42}$ and 3 $\times 10^{-36}$ cm$^{2}$ at a 90\% confidence level on spin-independent and spin-dependent WIMP-nucleon cross sections, respectively, at a WIMP mass ($m_χ$) of 5 GeV/${c}^2$ are achieved. The lower reach of $m_χ$ is extended to 2 GeV/${c}^2$.

hep-ex↗

arXiv2018

Characteristic Study and Development of Surface Resistivity Measuring Device for Resistive Plate Chamber Detector

The India-based Neutrino Observatory (INO) is an approved multi-institutional experiment of India. It will use maximum 30,000 Resistive Plate Chamber (RPC) of size 2x2m as an active detector in which each will be sandwiched between two iron plates. Each RPC detectors will be made up of 3mm thick glass (or Bakelite) plates whose one surface will be coated with graphite paint to work as electrode. To achieve effective and uniform electric field, the coated graphite paint must have uniform distribution over the glass surface. Uniformity can be demonstrated by measuring the surface resistance of the coated graphite paint. However, manual measurement of 60,000 electrodes with the help of multimeter and the jig demands huge amount of person-hour with compromised accuracy, and therefore that requires the need and importance of the automatic scanning system. An advanced automatic scanning system (ASS) has been designed & developed to fulfill the required needs and overcome the shortcomings of the initially developed system. Measurement are sensitive to the contact pressure between the jig and RPC electrode's surface. In this paper, various parameters of the ASS have been precisely fixed. Obtained results are compared with the standard one and found satisfactory within error. It has been observed that for obtaining the correct and safe value of surface resistance, applied pressure value in terms of force should be in the range of 9-11 Newton.

physics.ins-det↗

arXiv2018

Bulk and Surface Event Identification in p-type Germanium Detectors

The p-type point-contact germanium detectors have been adopted for light dark matter WIMP searches and the studies of low energy neutrino physics. These detectors exhibit anomalous behavior to events located at the surface layer. The previous spectral shape method to identify these surface events from the bulk signals relies on spectral shape assumptions and the use of external calibration sources. We report an improved method in separating them by taking the ratios among different categories of in situ event samples as calibration sources. Data from CDEX-1 and TEXONO experiments are re-examined using the ratio method. Results are shown to be consistent with the spectral shape method.

physics.ins-det↗

arXiv2016

Design and Performance of a Hybrid Fast and Thermal Neutron Detector

We report the performance and characterization of a custom-built hybrid detector consisting of BC501A liquid scintillator for fast neutrons and BC702 scintillator for thermal neutrons. The calibration and the resolution of the BC501A liquid scintillator detector are performed. The event identification via Pulse Shape Discrimination (PSD) technique is developed in order to distinguish gamma, fast and thermal neutrons. Monte Carlo simulation packages are developed in GEANT4 to obtain actual neutron energy spectrum from the measured recoil spectrum. The developed methods are tested by reconstruction of 241AmBe(α, n) neutron spectrum.

physics.ins-det↗

arXiv2016

Constraints on Axion couplings from the CDEX-1 experiment at the China Jinping Underground Laboratory

We report the results of searches for solar axions and galactic dark matter axions or axion-like particles with CDEX-1 experiment at the China Jinping Underground Laboratory, using 335.6 kg-days of data from a p-type point-contact germanium detector. The data are compatible with the background model and no excess signals are observed. Limits of solar axions on the model independent coupling $g_{Ae}<2.5\times10^{-11}$ from Compton, bremsstrahlung, atomic-recombination and deexcitation channel and $g^{\text{eff}}_{AN}\times g_{Ae}<6.1\times10^{-17}$ from $^{57}$Fe M1 transition at 90 % confidence level are derived. Within the framework of the DFSZ and KSVZ models, our results exclude the axion mass heavier than 0.9 eV/c$^{2}$ and 173 eV/c$^{2}$, respectively. The derived constraints for dark matter axions below 1 keV improves over the previous results.

hep-ex↗

arXiv2016

Characterization and Performance of Germanium Detectors with sub-keV Sensitivities for Neutrino and Dark Matter Experiments

Germanium ionization detectors with sensitivities as low as 100 eVee (electron-equivalent energy) open new windows for studies on neutrino and dark matter physics. The relevant physics subjects are summarized. The detectors have to measure physics signals whose amplitude is comparable to that of pedestal electronic noise. To fully exploit this new detector technique, various experimental issues including quenching factors, energy reconstruction and calibration, signal triggering and selection as well as evaluation of their associated efficiencies have to be attended. The efforts and results of a research program to address these challenges are presented.

physics.ins-det↗

arXiv2016

Measurement of Characteristic Impedance of Silicon Fiber Sheet based readout strips panel for RPC detector in INO

The India based Neutrino Observatory (INO) is a mega science project of India, which is going to use near about 30, 000 Resistive Plate Chambers (RPC) as active detector elements for the study of atmospheric neutrino oscillations. Each RPC detector will consist of two orthogonally placed readout strips panel for picking the signals generated in the gas chamber. The area of RPC detector in INO-ICAL (Iron Calorimeter) experiment will be 2m x 2m, therefore the dimension of readout strips panel will also be of 2m x 2m. To get undistorted signals pass through the readout strips panel to frontend electronics, their Characteristic Impedance should be matched with each other. For the matching of Characteristic Impedance we have used the principle of termination. In the present paper we will describe the need and search of new dielectric material for the fabrication of flame resistant, waterproof and flexible readout pickup strips panel. We will also describe the measurement of Characteristic Impedance of plastic honeycomb based readout strips panel and Silicon Fiber sheet based readout strips panel in a comparative way, and its variation under loading and with time.

physics.ins-det↗

arXiv2016

A Search of Low-Mass WIMPs with p-type Point Contact Germanium Detector in the CDEX-1 Experiment

The CDEX-1 experiment conducted a search of low-mass (< 10 GeV/c2) Weakly Interacting Massive Particles (WIMPs) dark matter at the China Jinping Underground Laboratory using a p-type point-contact germanium detector with a fiducial mass of 915 g at a physics analysis threshold of 475 eVee. We report the hardware set-up, detector characterization, data acquisition and analysis procedures of this experiment. No excess of unidentified events are observed after subtraction of known background. Using 335.6 kg-days of data, exclusion constraints on the WIMP-nucleon spin-independent and spin-dependent couplings are derived.

hep-ex↗

arXiv2015

Effect of Mg substitution in Sr2SiO4:Eu2+ nanophosphors for blue and white emission at near UV excitation

Nanophosphors of (Sr0.98-xMgxEu0.02)2SiO4 (x=0, 0.18, 0.38, 0.58 and 0.78) were prepared through low temperature solution combustion method and their luminescence properties were studied. The emission peak for Eu2+ doped Sr2SiO4 nanophosphor is observed at ~490 nm and ~553 nm corresponding to two Sr2+ sites Sr(I) and Sr(II) respectively for 395 nm excitation but the addition of Mg2+ dopant in Sr2SiO4 leads to suppression of ~553 nm emission peak due to absence of energy levels of Sr (II) sites which results in a single broad emission at ~460nm. It was shown that the emission peak blue shifted with increase in Mg concentration which may be attributed to change in crystal field environment around Sr(I) sites. Therefore the (Mg0.78Sr0.20Eu0.02)2SiO4: Eu2+ nanophosphor can be used for blue emission and the Sr2SiO4:Eu0.042+ for green-yellow emission at 395 nm excitations. The CIE coordinates for mixed powders of (Mg0.78Sr0.20Eu0.02)2SiO4 and Sr2SiO4:Eu0.042+ (in 1: 1 ratio) falls in the white region demonstrating the possible use of the mixture in white light generation using near UV excitation source.

cond-mat.mtrl-sci↗

arXiv2014

Limits on light WIMPs from the CDEX-1 experiment with a p-type point-contact germanium detector at the China Jingping Underground Laboratory

We report results of a search for light Dark Matter WIMPs with CDEX-1 experiment at the China Jinping Underground Laboratory, based on 53.9 kg-days of data from a p-type point-contact germanium detector enclosed by a NaI(Tl) crystal scintillator as anti-Compton detector. The event rate and spectrum above the analysis threshold of 475 eVee are consistent with the understood background model. Part of the allowed regions for WIMP-nucleus coherent elastic scattering at WIMP mass of 6-20 GeV are probed and excluded. Independent of interaction channels, this result contradicts the interpretation that the anomalous excesses of the CoGeNT experiment are induced by Dark Matter, since identical detector techniques are used in both experiments.

hep-ex↗

arXiv2014

Limits on light WIMPs with a germanium detector at 177 eVee threshold at the China Jinping Underground Laboratory

The China Dark Matter Experiment reports results on light WIMP dark matter searches at the China Jinping Underground Laboratory with a germanium detector array with a total mass of 20 g. The physics threshold achieved is 177 eVee ("ee" represents electron equivalent energy) at 50% signal efficiency. With 0.784 kg-days of data, exclusion region on spin-independent coupling with the nucleon is derived, improving over our earlier bounds at WIMP mass less than 4.6 GeV.

hep-ex↗

arXiv2013

First results on low-mass WIMP from the CDEX-1 experiment at the China Jinping underground Laboratory

The China Dark matter Experiment collaboration reports the first experimental limit on WIMP dark matter from 14.6 kg-day of data taken with a 994 g p-type point-contact germanium detector at the China Jinping underground Laboratory where the rock overburden is more than 2400 m. The energy threshold achieved was 400 eVee. According to the 14.6 kg-day live data, we placed the limit of N= 1.75 * 10^{-40} cm^{2} at 90% confidence level on the spin-independent cross-section at WIMP mass of 7 GeV before differentiating bulk signals from the surface backgrounds.

hep-ex↗

arXiv2013

Modification in structural, dielectric and magnetic properties of La and Nd co-substituted epitaxial BiFeO3 thin films

The influence of La and Nd co-substitution on the structural and magnetic properties of BiFeO3 (BFO) thin films was examined. Epitaxial thin films of pure and, La and Nd co-doped BFO on the SrRuO3 buffered single crystal SrTiO3 (001) substrate were deposited using pulsed laser deposition. The structural change in co doped La and Nd BFO thin films which was caused by the changes of force constant in the crystal lattice induced by ionic radii mismatch was investigated. Raman spectroscopy studies manifest the structural change in doped BFO films from rhombohedral to monoclinic distorted phase which is induced by the co substitution of La and Nd. Room temperature magnetic hysteresis curves indicated that saturation magnetization is enhanced in the doped film with saturation magnetization of ~20 emu/cm3. The dielectric and magnetic properties are effectively improved in BLNFO films compared to pure BFO thin films.

cond-mat.mtrl-sci↗

arXiv2013

Characteristics of Compound Multiplicity in 84^Kr_36 with various light and heavy targets at 1 GeV per nucleon

Present article focuses on the interactions of 84 Kr 36 having kinetic energy around 1 GeV per nucleon with NIKFI BR2 nuclear emulsion detectors targets, that can reveal important features of some compound multiplicity. The observation showed that the width of the compound multiplicity distributions and value of the mean compound multiplicity have linear relation with the mass number of the projectile as well as colliding system.

nucl-ex↗

arXiv2011

Emission Characteristics of the Projectile Fragments at Relativistic Energy

A projectile (84^Kr_36) having kinetic energy around 1 A GeV was used to expose NIKFI BR-2 emulsion target. A total of 700 inelastic events are used in the present studies on projectile fragments. The emission angle of the projectile fragments are strongly affected by charge of the other projectile fragments emitted at same time with different emission angle is observed. The angular distribution studies show symmetrical nature for lighter charge projectile fragments. The symmetrical nature decreased with the charge of projectile fragments. At ~4o of emission angle for double charge projectile fragments, the momentum transfer during interaction is similar for various target species of emulsion were observed. We also observed a small but significant amplitude peaks on both side of the big peak for almost all light charge projectile fragments having different delta angle values. It reflects that there are few percent of projectile fragments that are coming from the decay of heavy projectile fragments or any other process.

nucl-ex↗

arXiv2010

Two source emission behaviour of alpha fragments of projectile having energy around 1 GeV per nucleon

The emission of projectile fragments alpha has been studied in ^{84}Kr interactions with nuclei of the nuclear emulsion detector composition at relativistic energy below 2 GeV per nucleon. The angular distribution of projectile fragments alpha in terms of transverse momentum could not be explained by a straight and clean-cut collision geometry hypothesis of Participant - Spectator (PS) Model. Therefore, it is assumed that projectile fragments alpha were produced from two separate sources that belong to the projectile spectator region differing drastically in their temperatures. It has been clearly observed that the emission of projectile fragments alpha are from two different sources. The contribution of projectile fragments alpha from contact layer or hot source is a few percent of the total emission of projectile fragments alphas. Most of the projectile fragments alphas are emitted from the cold source. It has been noticed that the temperature of hot and cold regions are dependent on the projectile mass number.

hep-ex↗

arXiv2010

Characteristics of alpha projectile fragments emission in interaction of nuclei with emulsion

The properties of the relativistic alpha fragments produced in interactions of 84^Kr at around 1 A GeV in nuclear emulsion are investigated. The experimental results are compared with the similar results obtained from various projectiles with emulsion interactions at different energies. The total, partial nuclear cross-sections and production rates of alpha fragmentation channels in relativistic nucleus-nucleus collisions and their dependence on the mass number and initial energy of the incident projectile nucleus are investigated. The yields of multiple alpha fragments emitted from the interactions of projectile nuclei with the nuclei of light, medium and heavy target groups of emulsion-detector are discussed and they indicate that the projectile-breakup mechanism seems to be free from the target mass number. It is found that the multiplicity distributions of alpha fragments are well described by the Koba-Nielsen-Olesen (KNO) scaling presentation. The mean multiplicities of the freshly produced newly created charged secondary particles, normally known as shower and secondary particles associated with target in the events where the emission of alpha fragments were accompanied by heavy projectile fragments having Z value larger than 4 seem to be constant as the alpha fragments multiplicity increases, and exhibit a behavior independent of the alpha fragments multiplicity.

nucl-ex↗