Satyajit Saha

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Simulation of Nuclear Recoils due to Supernova Neutrino-induced Neutrons in Liquid Xenon Detectors

Journal of Physics: Conference Series

Neutrinos from supernova (SN) bursts can give rise to detectable number of nuclear recoil (NR) ev... more Neutrinos from supernova (SN) bursts can give rise to detectable number of nuclear recoil (NR) events through the coherent elastic neutrino-nucleus scattering (CEυNS) process in large scale liquid xenon detectors designed for direct dark matter search, depending on the SN progenitor mass and distance. Here we show that in addition to the direct NR events due to CEvNS process, the SN neutrinos can give rise to additional nuclear recoils due to the elastic scattering of neutrons produced through inelastic interaction of the neutrinos with the xenon nuclei. We find that the contribution of the supernova neutrino-induced neutrons (υIn) can significantly modify the total xenon NR spectrum at large recoil energies compared to that expected from the CEυNS process alone. Moreover, for recoil energies ≳ 20 keV, dominant contribution is obtained from the (υIn) events. We numerically calculate the observable S1 and S2 signals due to both CEvNS and vIn processes for a typical liquid xenon based...

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Effect of Electric Field and Gas Mixture on RPC Time Resolution

Springer Proceedings in Physics

A large number of Resistive Plate Chamber will be used in the ICAL detector setup in the proposed... more A large number of Resistive Plate Chamber will be used in the ICAL detector setup in the proposed INO facility. The timing response from RPCs will govern the accuracy of ICAL in distinguishing the up-going muon tracks from the down-going ones by recording the time of passage of the muons through the RPCs. The timing performance of a bakelite RPC has been studied both experimentally and numerically to understand the effect of different operating conditions, like applied voltage and used gas mixture, on the timing properties. This can lead us to judge the suitability of bakelite RPC for application in ICAL setup which is planned to be equipped with glass RPCs at present.

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Simulation of neutron background for DINO Dark Matter search experiment

The goal of the proposed Dark Matter (DM) search experiment DINO (Dark matter@INO) is to search f... more The goal of the proposed Dark Matter (DM) search experiment DINO (Dark matter@INO) is to search for the Weakly Interacting Massive Particles (WIMP) as candidates of Dark Matter. WIMPs are expected to interact with the detector nuclei via elastic scattering, resulting in nuclear recoils. DINO experiment proposes to use suitable scintillation detectors operated at cryogenic temperature for the detection of recoiling nuclei. Such rare event search needs high sensitivity and complete knowledge about the possible radiation background that can interfere with the experiment.

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$Research paper thumbnail of Comparison of Electromagnetically Induced Transparency (EIT) Spectra for Six-level Lambda $(\Lambda)$ and Five-level V-type Systems$

Comparison of Electromagnetically Induced Transparency (EIT) Spectra for Six-level Lambda $(\Lambda)$ and Five-level V-type Systems

Electromagnetically induced transparency (EIT) is experimentally studied in a rubidium vapour cel... more Electromagnetically induced transparency (EIT) is experimentally studied in a rubidium vapour cell (without buffer gas, both $^{87}$Rb and $^{85}$Rb present according to their natural abundance) kept within two-layers of $\mu(\mu)$-metal shields to avoid the effect of Earth's magnetic field on the energy levels of atomic rubidium. An external cavity diode laser (ECDL), used as a low power probe laser, is locked to the hyperfine cross-over peak of $F = 2 \rightarrow F' = 2, 3$ transitions of $^{87}$Rb. The frequency of another ECDL, the pump laser, is set to scan the $F=1 \rightarrow F' = 0, 1, 2$ transitions of $^{87}$Rb. These form the $\Lambda$-type six level system. In the V-type system, both the pump and the probe lasers share the same $F = 2$ ground level. The probe beam coming out of the cell is detected by a low noise fast photodetector. The resulting spectra show signature of EIT in the "peak" for the $\Lambda$-type system and in...

Supernova neutrino induced neutrons in liquid xenon dark matter detectors

Neutrinos from supernova (SN) bursts can give rise to detectable number of nuclear recoil (NR) ev... more Neutrinos from supernova (SN) bursts can give rise to detectable number of nuclear recoil (NR) events through the process of coherent elastic neutrino-nucleus scattering (CEνNS) in future large (multi-ton scale) liquid xenon detectors employed for dark matter search depending on the SN progenitor mass and distance to the SN event. Here we point out that in addition to the direct NR events due to CEνNS process, there is a secondary source of nuclear recoils due to elastic scattering of the neutrons produced through inelastic neutrino-nucleus scattering of the supernova neutrinos with the target xenon nuclei. We estimate the contribution of these supernova neutrinoinduced neutrons (νIn) to the total xenon NR spectrum and find that the latter can be significantly modified at large recoil energies from that expected from the CEνNS process alone, with the νIn contribution dominating the total integral recoil energy spectrum for recoil energies ∼ 20 keV. With the capability to measure the...

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Detecting supernova neutrinos with iron and lead detectors

Physical Review D

Supernova (SN) neutrinos can excite the nuclei of various detector materials beyond their neutron... more Supernova (SN) neutrinos can excite the nuclei of various detector materials beyond their neutron emission thresholds through charged current (CC) and neutral current (NC) interactions. The emitted neutrons, if detected, can be a signal for the supernova event. Here we present the results of our study of SN neutrino detection through the neutron channel in 208 Pb and 56 Fe detectors for realistic neutrino fluxes and energies given by the recent Basel/Darmstadt simulations for a 18 solar mass progenitor SN at a distance of 10 kpc. We find that, in general, the number of neutrons emitted per kTon of detector material for the neutrino luminosities and average energies of the different neutrino species as given by the Basel/Darmstadt simulations are significantly lower than those estimated in previous studies based on the results of earlier SN simulations. At the same time, we highlight the fact that, although the total number of neutrons produced per kTon in a 56 Fe detector is more than an order of magnitude lower than that for 208 Pb, the dominance of the flavor blind NC events in the case of 56 Fe, as opposed to dominance of νe induced CC events in the case of 208 Pb, offers a complementarity between the two detector materials so that simultaneous detection of SN neutrinos in a 208 Pb and a sufficiently large 56 Fe detector suitably instrumented for neutron detection may allow estimating the fraction of the total µ and τ flavored neutrinos in the SN neutrino flux and thereby probing the emission mechanism as well as flavor oscillation scenarios of the SN neutrinos.

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Spectroscopic investigations of L -shell ionization in heavy elements by electron impact

Journal of Quantitative Spectroscopy and Radiative Transfer

Abstract The absolute L subshell specific electron impact ionization cross sections near the ioni... more Abstract The absolute L subshell specific electron impact ionization cross sections near the ionization threshold ( 16 E 45 keV ) of lead and thorium are obtained from the measured L X-ray production cross sections. Monte Carlo simulation is done to account for the effect of the backscattered electrons, and the final experimental results are compared with calculations performed using distorted wave Born approximation and the modified relativistic binary encounter Bethe model. The sensitivity of the results on the atomic parameters is explored. Observed agreements and discrepancies between the experimental results and theoretical estimates, and their dependence on the specific atomic parameters are reported.

Observation of electromagnetically induced transparency in six-level Rb atoms and theoretical simulation of the observed spectra

Journal of Physics B: Atomic, Molecular and Optical Physics, 2015

We report the observation of electromagnetically induced transparency (EIT) in a six-level Λ-type... more We report the observation of electromagnetically induced transparency (EIT) in a six-level Λ-type system in atomic Rb vapor containing both 87Rb and 85Rb. The experimental observation includes five velocity selective optically pumped (VSOP) absorption dips for both 87Rb and 85Rb. The EIT signal appears on the background of one such VSOP absorption dips. The measured EIT linewidth () shows sub-natural ( ) values for both lower and higher values of pump Rabi-frequencies. The density matrix based theoretical model for the six-level system is developed and solved numerically by taking into account the Doppler broadening. A complete analytical solution (non perturbative) for a three level Λ-type system has been obtained and compared with the experimentally observed sub-natural EIT linewidth. The simulated spectra are in good agreement with the experimental findings.

Observation of a rare cosmic ray event at mountain altitude

Astroparticle Physics, 2015

ABSTRACT Existence of strangelets in cosmic rays has been predicted even at mountain altitudes ∼3... more ABSTRACT Existence of strangelets in cosmic rays has been predicted even at mountain altitudes ∼3-4km∼3-4km with extremely low abundance. We exposed an appropriate passive detector to cosmic rays at Darjeeling, India, at an atmospheric pressure of 765 hPa, as a pilot study to determine its suitability for the detection of strangelets in a large area detector array through long-term exposure. During the analysis we found a highly unusual event consisting of a cluster of six identical nuclear tracks. We argue that even the most mundane explanation of this event requires unusual physics, the first possible observation of multifragmentation involving cosmic rays.

INO prototype detector and data acquisition system

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2009

India-based Neutrino Observatory (INO) collaboration is proposing to build a 50 kton magnetised i... more

Electric field distribution and simulation of avalanche formation due to the passage of heavy ions in a parallel grid avalanche counter

Pramana, 2009

Electric field distributions and their role in the formation of avalanche due to the passage of h... more Electric field distributions and their role in the formation of avalanche due to the passage of heavy ions in parallel grid avalanche type wire chamber detectors are evaluated using a Monte Carlo simulation. The relative merits and demerits of parallel and crossed wire grid configurations are studied. It is found that the crossed grid geometry has marginally higher gain at larger electric fields close to the avalanche region. The spatial uniformity of response in the two wire grid configurations is also compared.

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MEGHNAD — A multi element detector array for heavy ion collision studies

Pramana, 2001

In the coming decade, the expanding field of experimental nuclear physics in our country is going... more In the coming decade, the expanding field of experimental nuclear physics in our country is going to see a quantum leap in research and developmental activities with new accelerator facilities like the variable energy cyclotron with ECR heavy ion source, the upcoming K-500 superconducting cyclotron, both at VECC, Calcutta, and the superconducting linac boosters at both the Pelletron Accelerator Facilities at TIFR, Mumbai and NSC, New Delhi. When heavy ion beam available from such machines fall on a target and undergo collision, very rich and often pristine fields of research open up. In order to carry on such activities, we have taken up a project to build a multi element gamma, heavy ion and neutron array of detectors (MEGHNAD) to detect and study the properties of a wide variety of particles like neutrons, protons, light mass clusters, massive ejected fragments, and gamma rays with good solid angle coverage and efficiency. Design of the detector array, performance of the prototype detector and brief outline of the research programme to be undertaken with the detector array will be discussed.

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Electric field distribution and simulation of avalanche formation due to the passage of heavy ions in a parallel grid avalanche counter

Pramana-journal of Physics - PRAMANA-J PHYS, 2009

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INO Prototype Detector and Data Acquisition System

Nuclear Inst. and …, 2009

India-based Neutrino Observatory (INO) collaboration is proposing to build a 50 kton magnetised i... more

A method to study heavy ion reactions using position sensitive and Bragg curve spectroscopy detectors

Nuclear Instruments and …, 1993

A large area Bragg curve spectroscopy (BCS) detector and a position sensitive parallel grid avala... more A large area Bragg curve spectroscopy (BCS) detector and a position sensitive parallel grid avalanche counter have been developed to study heavy ion reactions, such as inelastic excitations and few nucleon transfer reactions near the Coulomb barrier. Reasonably good resolutions have been achieved for energy, atomic number and angle. A theoretical investigation on the mass dependence of the Bragg peak signal from the BCS detector, shows that there is a negligible mass dependence related to the geometry of the detector. The mass number of the heavy ions which cannot be obtained by the above method, has been identified by detecting the corresponding characteristic gamma rays from the product nuclei with two large solid angle gamma ray detectors.

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