arXiv subjects

V. S. Pantuev

Publications and source records attributed to V. S. Pantuev.

At least 19 recordsLinked to original sources

arXiv2024

Contribution of gaseous tritium source rear wall to tritium beta-spectrum in Troitsk nu-mass experiment

We avaluate the contribution of electron scattering on the rear wall of a windowless gaseous tritium source in the Troitsk nu-mass setup. There is a finite probability for them to scatter, return back and reach the detector. A such additional component distorts the measured electron spectrum. We calculate the scattering on the rear side of the vacuum pipe by the GEANT4 simulation and trace the electrons back through the magnetic fields to the spectrometer and registration system. The contribution is a few orders of magnitude smaller compared to the original spectrum at the end of the beta-spectrum of 18.6 keV but reaches 2\% at 11 keV. Taking into account this rear wall scattering we can fit well the measured spectrum in search for a sterile neutrino component in the tritium beta decay.

physics.ins-det↗

arXiv2022

Calibration of Troitsk nu-mass detector readout electronics by signal digital filters

We present the results of tuning and calibration of the detector electronics in the signal digitization mode. The goal of the experiment is to search for a possible sterile neutrino signature in tritium beta-decay. The read-out electronics work in direct oscilloscope mode, which requires to optimize time frame the with the goal to minimize noise and energy resolution. We use a 7-pixel silicon drift detector (SDD) and a CMOS charge sensitive preamplifier with very low integration capacitor. Amplifier forms a slowly rising output shape and operates in pulse-reset mode. The 125 MHz ADC digitizes the signals. Using calibration data from Fe55 and Am241 gamma sources we check triangular and trapezoid digital filters to obtain the best noise and energy resolution performance. We are also examining the option to differentiate the output signal.

physics.ins-det↗

arXiv2021

Analysis of published data of electron capture in 7Be in the search for a heavy neutrino in the mass range under 800 keV

We present a reanalysis of the experimental data of electron capture in $^7$Be embedded in Ta which have been published by other authors. Our goal is to set upper limits on a mixture of electron neutrino with a possible right-handed heavy neutrino in the 150--800 keV mass range. In the published experiment a $^7$Li recoil energy spectrum in the 20--200 eV range was measured. In case of electron capture with emission of a heavy neutrino, the recoil spectrum should be shifted to the lower energies. We search for an additional Gauss-shaped structure with the same energy width as the main K-shell transition peak. For this we digitize the published spectrum curve, find the energy resolution, calculate the moving sum of the events along the spectrum in the energy interval of about 3 sigma of energy resolution. Then we use the statistical error of this sum to exclude at some level the appearance of an additional peak. Finally, we present the upper limits at a 95\% confidence level on electron neutrino -- heavy neutrino mixing element, $U^2$, in the mass matrix. New upper limits are at least one order of magnitude lower than the existing data in 300--800 keV mass range.

hep-ex↗

arXiv2020

Characterization of Silicon Drift Detectors with Electrons for the TRISTAN Project

Sterile neutrinos are a minimal extension of the Standard Model of Particle Physics. A promising model-independent way to search for sterile neutrinos is via high-precision beta spectroscopy. The Karlsruhe Tritium Neutrino (KATRIN) experiment, equipped with a novel multi-pixel silicon drift detector focal plane array and read-out system, named the TRISTAN detector, has the potential to supersede the sensitivity of previous laboratory-based searches. In this work we present the characterization of the first silicon drift detector prototypes with electrons and we investigate the impact of uncertainties of the detector's response to electrons on the final sterile neutrino sensitivity.

physics.ins-det↗

arXiv2020

Detritiation of the electrostatic spectrometer of Troitsk Nu-mass experiment

The paper describes methods and presents results of the Troitsk Nu-mass experiment spectrometer cleanup, which inner volume (40 m3) and surfaces (160 m2) was contaminated by 4.4 GBq of tritium. The Troitsk Nu-mass experiment of Institute for Nuclear Research of Russian Academy of Sciences, Moscow, is designed to measure the spectrum of electrons from tritium decays in order to search for hypothetical particles - sterile neutrinos. As a result of equipment failure, the spectrometer internal volume was contaminated with tritium. The contamination made measurements impossible and the research program stopped. The methods of vacuum extraction, hydrogen soaks, and water vapour soaks were used for cleanup. As a result of detritiation, the background level of the main detector of the Troitsk Nu-mass spectrometer decreased by more than 10 times, which made it possible to resume work. The results are consistent with the data obtained earlier for volumes in normal conditions in the air and can be used for planning work on detritiation of similar installations.

physics.ins-det↗

arXiv2017

Corona effect in AA collisions at LHC

Following our earlier finding based on RHIC data on the dominant jet production from nucleus corona region, we reconsider this effect in nucleus-nucleus collisions at LHC energy. Our hypothesis was based on experimental data, which raised the idea of a finite formation time for the produced medium. At RHIC energy and in low density corona region this time reaches about 2 fm/c. All observed high p_t particles are produced in the corona region and have a chance to escape during this 2 fm/c. After that, the formed high density matter absorbs all jets. Following this hypothesis, the nuclear modification factor R_{AA} should be independent on particle momentum and be flat versus p_t. At the same time, we describe the finite azimuthal anisotropy of high p_t particles, v_2. A separate prediction held that, at LHC energy, the formation time in the corona region should be two times smaller, about 1 fm/c. New data at LHC show that R_{AA} is not flat and is rising with p_t. We add to our original hypothesis an assumption that a fast parton traversing the produced medium loses the fixed portion of its energy. A shift of about 7 GeV (I would call it as a parton binding energy) from the original power law p^{-6} production cross section in pp explains well all the observed R_{AA} dependencies. The shift of about 7 GeV is also valid at RHIC energy, where the cross section follows a power law with about p^{-8} and this shift explains a very slow rise of R_{AA} seen for neutral pions with p_t above 15 GeV/c. We also show that the observed at LHC dependence of v_2 at high p_t and our previous predictions agree.

hep-ph↗

arXiv2017

First measeurements in search for keV-sterile neutrino in tritium beta-decay by Troitsk nu-mass experiment

We present the first measurements of tritium beta-decay spectrum in the electron energy range 16-18.6 keV. The goal is to find distortions which may correspond to the presence of a heavy sterile neutrinos. A possible contribution of this kind would manifest itself as a kink in the spectrum with a similar shape but with end point shifted by the value of a heavy neutrino mass. We set a new upper limits to the neutrino mixing matrix element U^2_{e4} which improve existing limits by a factor from 2 to 5 in the mass range 0.1-2 keV.

hep-ex↗

arXiv2017

A White Paper on keV Sterile Neutrino Dark Matter

We present a comprehensive review of keV-scale sterile neutrino Dark Matter, collecting views and insights from all disciplines involved - cosmology, astrophysics, nuclear, and particle physics - in each case viewed from both theoretical and experimental/observational perspectives. After reviewing the role of active neutrinos in particle physics, astrophysics, and cosmology, we focus on sterile neutrinos in the context of the Dark Matter puzzle. Here, we first review the physics motivation for sterile neutrino Dark Matter, based on challenges and tensions in purely cold Dark Matter scenarios. We then round out the discussion by critically summarizing all known constraints on sterile neutrino Dark Matter arising from astrophysical observations, laboratory experiments, and theoretical considerations. In this context, we provide a balanced discourse on the possibly positive signal from X-ray observations. Another focus of the paper concerns the construction of particle physics models, aiming to explain how sterile neutrinos of keV-scale masses could arise in concrete settings beyond the Standard Model of elementary particle physics. The paper ends with an extensive review of current and future astrophysical and laboratory searches, highlighting new ideas and their experimental challenges, as well as future perspectives for the discovery of sterile neutrinos.

hep-ph↗

arXiv2016

Electron scattering on hydrogen and deuterium molecules at 14-25 keV by the "Troitsk nu-mass" experiment

We've performed precise measurements of electron scattering on molecular hydrogen and deuterium by using the "Troitsk nu-mass" setup. Electrons were generated by the electron gun with an energy line width better than 0.3 eV. The electron energies were 14, 17, 18.7, 19 and 25 keV. The windowless gaseous tritium source (WGTS) was filled by hydrogen isotopes and served as a target. The total column density was adjusted to form a length of 0.35--0.7 of the electron mean free path. The integral spectrum of scattered electrons was measured by the electrostatic spectrometer with a magnetic adiabatic collimation and relative energy resolution 8.3 10^{-5}. As a result, the shapes of molecular excitation and ionization spectra were extracted for both isotopes. We did not find any difference between hydrogen and deuterium targets. The relative energy dependence was extracted too.

physics.ins-det↗

arXiv2015

The role of electron scattering from registration detector in a MAC-E type spectrometer

There is a proposal to search for a sterile neutrino in a few keV mass range by the "Troitsk nu-mass" facility. In order to estimate sterile neutrino mixing one needs to make precision spectrum measurements well below the endpoint using the existing electrostatic spectrometer with a magnetic adiabatic collimation, or MAC-E filter. The expected signature will be a kink in the electron energy spectrum in tritium beta-decay. In this article we consider the systematic effect of electron backscattering on the detector used in the spectrometer. For this purpose we provide a set of Monte-Carlo simulation results of electron backscattering on a silicon detector with a thin golden window with realistic electric and magnetic fields in the spectrometer. We have found that the probability of such an effect reaches up to 20-30\%. The scattered electron could be reflected backwards to the detector by electrostatic field or by magnetic mirror. There is also a few percent probability to escape from the spectrometer through its entrance. A time delay between the scattering moment on the detector and the return of the reflected electron can reach a couple of microseconds in the Troitsk spectrometer. Such estimations are critical for the planning upgrades of the detector and the registration electronics.

physics.ins-det↗

arXiv2015

The current status of "Troitsk nu-mass" experiment in search for sterile neutrino

We propose a new experiment to search for a sterile neutrino in a few keV mass range at the "Troitsk nu-mass" facility. The expected signature corresponds to a kink in the electron energy spectrum in tritium beta-decay. The new goal compared to our previous experiment will be precision spectrum measurements well below end point. The experimental installation consists of a windowless gaseous tritium source and a high resolution electromagnetic spectrometer. We estimate that the current bounds on the sterile neutrino mixing parameter can be improved by an order of magnitude in the mass range under 5 keV without major upgrade of the existing equipment. Upgrades of calibration, data acquisition and high voltage systems will allow to improve the bounds by another order of magnitude.

physics.ins-det↗

arXiv2014

A search for an additional neutrino mass eigenstate in 2 to 100 eV region from "Troitsk nu-mass" data - detailed analysis

In this paper we present the details of our previously published results for a search for an additional neutrino mass state in $β$-electron spectrum from the Troitsk nu-mass experiment. Here we present steps of the analysis, show a set of likelihood functions obtained for each additional heavy mass value. We demonstrate how systematic errors were estimated. We also compare our results with those published recently for a similar analysis for Mainz data and try to explain why there is a factor of 2-3 difference in the sensitivity for an additional heavy mass.

hep-ex↗

arXiv2012

An upper limit on additional neutrino mass eigenstate in 2 to 100 eV region from "Troitsk nu-mass" data

We performed a search for any sign of an additional neutrino mass state in beta-electron spectrum based on data reanalysis of direct electron antineutrino mass measurements in Tritium beta-decay in the Troitsk nu-mass experiment. The existing data set allows us to search for such a state in the mass range up to 100 eV. The lowest value at a 95% C.L. upper limit for the contribution of a heavy eigenstate into electron neutrino is around or less than 1% for masses above 20 eV.

hep-ex↗

arXiv2011

An upper limit on electron antineutrino mass from Troitsk experiment

An electron antineutrino mass has been measured in tritium beta-decay in the "Troitsk nu-mass" experiment. The setup consists of a windowless gaseous tritium source and an electrostatic electron spectrometer. The whole data set acquired from 1994 to 2004 was reanalysed. A thorough selection of data with the reliable experimental conditions has been performed. We checked every known systematic effect and got the following experimental estimate for neutrino mass squared m_{nu}^{2}=-0.67+/- 2.53 {eV}^{2}. This gives an experimental upper sensitivity limit of m_{nu}<2.2 eV and upper limit estimates m_{nu}<2.12 eV, 95% C.L. for Bayesian statistics and m_{nu}<2.05 eV, 95% C.L. for the Feldman and Cousins approach.

hep-ex↗

arXiv2011

Empirical estimation the effects of flow on thermal photon angular distribution and spectra in nucleus-nucleus collisions at RHIC and LHC

Experimental data for hadron radial and elliptic flow are used to investigate their influence on the shape of the thermal photon spectrum at RHIC. Leaving alone the actual mechanism of photon production and its time evolution, we concentrate on the spectrum shape. Radial and longitudinal flow of the bulk can change significantly the observed photon energy spectrum via the Doppler Effect. Experimental thermal photon data are described by local frame temperature parameter which depends on the assumption of longitudinal and radial flow. From the observed hadron elliptic flow we estimate the modulation of radial flow parameter versus the angle relative to the reaction plane. Based on this we calculate elliptic flow parameter for thermal photons, which was found to be very close to that for hadrons. Considering very similar amplitude for hadron elliptic flow at LHC and RHIC, we demonstrate that thermal photons at LHC should show large elliptic flow as well. All of these considerations are also valid for the low invariant mass dilepton pairs.

nucl-ex↗

arXiv2009

Prior to "Quark Matter 2006" predictions within retarded jet absorption scenario at RHIC

Predictions for some experimental physical observables in nucleus-nucleus collisions at RHIC energies are presented. I utilize the previous suggestion that the retarded, by time about 2-3 fm/c, jet absorption in opaque core is a natural explanation of many experimental data. This assumption is applied only to the particles with high transverse momentum above 4 GeV/c resulting from parton fragmentation. I calculate nuclear modification factor $R_{AA}$, $R_{AA}$ in- and out of the reaction plane, azimuthal anisotropy parameter $v_2$, jet suppression $I_{AA}$ for the away side jet and its dependence versus the reaction plane orientation. The systems under consideration are Au+Au, Cu+Cu, at 200 GeV and 62 GeV. Most of numbers are predictions prior to the QM2006.

nucl-ex↗

arXiv2007

"Jet-Ridge" effect in heavy ion collisions as a back splash from stopped parton

I propose a simple explanation of the ``ridge'' seen in the near-side jet two-particle correlation function in heavy ion collisions at RHIC. This could be a cumulative shock wave produced in liquid-like matter by an energetic stopped parton. Splash of liquid in the direction opposite to the fast penetrating object is a known effect. In nucleus-nucleus collision the trigger is an escaped non-interacting parton. Partner parton could be stopped in the medium forming a conical-like shock wave with density depletion behind the stopped parton. In the proposed scenario shock waves will move in three directions: two waves will form a correlation structure at angles differ from phi = 3.14 radians and are usually called a Mach Cone. The other direction is exactly opposite to the original direction of stopping parton. The wide rapidity distribution of the ridge is caused by the rapidity swing of the away-side jet and longitudinal expansion of the system along the beam direction. The calculation of such a shock wave is very complicated, but some phenomenological observables could be explained and predicted.

hep-ph↗

arXiv2007

Thermal Dileptons at LHC

We predict dilepton invariant-mass spectra for central 5.5 ATeV Pb-Pb collisions at LHC. Hadronic emission in the low-mass region is calculated using in-medium spectral functions of light vector mesons within hadronic many-body theory. In the intermediate-mass region thermal radiation from the Quark-Gluon Plasma, evaluated perturbatively with hard-thermal loop corrections, takes over. An important source over the entire mass range are decays of correlated open-charm hadrons, rendering the nuclear modification of charm and bottom spectra a critical ingredient.

hep-ph↗