bluuebunny/crossref_metadata_2025 huggingface dataset:
QCD phase diagram with chiral imbalance in NJL model: duality and lattice QCD results
Authors: Khunjua T G , Klimenko K G , Zhokhov Roman N
Published: November 2019

In addition to temperature and baryon chemical potential there exist other parameters that are essential in the real quark matter. One of them is isospin asymmetry, which does exist in nature, for example, in the compact stars or in heavy ion collisions. Chiral imbalance, the difference between left- and right-handed quarks, is another phenomenon that could occur in quark matter. We have shown that lattice QCD results support the existence of the approximate duality (found in effective models) in real QCD. The rise of pseudo-critical temperature with increase of chiral chemical potential μ
5 (the much debated effect recently, a lot of studies on this contradict each other) has been established in terms of just duality notion, hence reinforce confidence in this result and put it on the considerably more solid ground.
Search for critical behavior of strongly interacting matter in the NA61/SHINE experiment
Authors: Prokhorova Daria
Published: November 2019

NA61/SHINE is a fixed-target experiment at CERN SPS which studies strongly interacting matter. The search for experimental signatures of the critical point is performed via a comprehensive two-dimensional scan of the phase diagram of strongly interacting matter by changing beam momenta (13A - 150A GeV/c) and the size of colliding systems (p+p, p+Pb, Be+Be, Ar+Sc, Xe+La, Pb+Pb). Recent NA61/SHINE results on the search for critical behavior search in two-particle correlations, multiplicity and transverse momentum fluctuations, femtoscopy studies and intermittency analysis were presented.
NA61/SHINE experiment at CERN SPS: Recent results, current status and perspectives
Authors: Brzychczyk Janusz
Published: November 2019

The NA61/SHINE experiment at the CERN SPS studies hadron production properties in hadron-nucleus and nucleus-nucleus collisions. Recent results from p+p, Be+Be and Ar+Sc interactions provide new data on the system size and energy dependence of hadron multiplicities, spectra and fluctuations. In particular, they indicate a threshold for formation of large clusters interpreted as the onset of fireball. A scaled-factorial-moment analysis of the proton density fluctuations in Ar+Sc collisions at 150A GeV/c shows an intermittency signal, which may be a first trace of critical behavior. The main objective of the future NA61/SHINE program is to obtain high-precision data on charm hadron production. This new program is planed to start in 2021, after the Long Shutdown 2 of the CERN accelerators. It requires significant upgrades of the NA61/SHINE detectors in order to increase the data readout rate tenfold.
Coherent J/ψ photoproduction in ultra-peripheral Pb–Pb collisions with ALICE at the LHC
Authors: Lavicka Roman
Published: November 2019

There are several predictions for the behaviour of the gluon distribution in nuclei at small Bjorken-x and experimental data are needed to choose among them. This is achieved by measuring the cross section of processes specially sensitive to this parton distribution.

The high flux of photons from lead ions at the LHC allows us to study photon-induced reactions in ultra-peripheral collisions of Pb–Pb nuclei, in particular of those producing a J/ψ meson exclusively. The study of these collisions, where projectiles do not overlap, provides information about the initial state of nuclei.

The newest ALICE results on vector meson photoproduction are presented. The increased statistics and higher collision energy of

s

N
N

=
5.02

TeV

of Run 2 allow us to put new constraints on available models.
Femtoscopic scales of particle-emitting source in small and large systems
Authors: Semenova V K , Khyzhniak E V , Nigmatkulov G A
Published: November 2019

The femtoscopy technique allows one to measure the spatial and temporal scales of the particle-emitting source produced in high-energy collisions. In non-central ultra-relativistic heavy-ion collisions, emitting source may be tilted in the reaction plane. The orientation of freeze-out distributions is interesting because it provides complementary information about quark-gluon matter properties. In the experiment, the tilt can be extracted by measuring femtoscopic radii as a function of the pair angle with respect to the first-order event plane.

In this talk, we will present results of azimuthally sensitive femtoscopic analysis of Au+Au and Cu+Au collisions at

s

N
N

=
200

GeV

. We will also present the transverse momentum and multiplicity dependence of identical pion femtoscopic radii from d+Au, 3He+Au collisions at

s

N
N

=
200

GeV

. All data was obtained from the UrQMD model.
Heavy Flavor Physics at ATLAS and CMS
Authors: Chistov Ruslan
Published: November 2019

In this talk I report recent results on heavy flavor physics from ATLAS and CMS. It includes two topics: spectroscopy of open or hidden beauty hadrons and studies of rare B decays of the type b → sμ+μ−
. The former one is aimed to collect new information on the properties of beauty hadrons which helps to gain better understanding of QCD. And the latter one provides a good opportunity of searching for New Physics, the effects beyond the Standard Model. The discussed results were obtained with the Run 1 data

(

s

=
8

TeV
)

or Run 2 data

(

s

=
13

TeV
)

.
Hadronic production of double charmed baryons with excited diquark
Authors: Berezhnoy A V , Belov I N , Likhoded A K
Published: November 2019

We discuss the prospects of the observation of double heavy baryons Ξ
cc
, Ω
cc
with excited diquark (S and P excitations) in experiments at LHC. P-wave excitations of a diquark in double charmed baryons are supposed to be quite narrow since their decay into the ground state is highly suppressed. Relative yields of S-wave and P-wave excitations have been estimated within pQCD for the LHCb kinematics.
Reconstruction techniques in Supersymmetry searches with the ATLAS detector
Authors: Vermeulen Ambrosius
Published: November 2019

Many supersymmetric scenarios of the Standard Model feature final states which are difficult for standard particle reconstruction. The production of massive sparticles can for example lead to the production of boosted quarks or vector bosons. At the same time, transitions between nearly mass-degenerate sparticles challenges the standard event reconstruction because of the presence of very soft leptons or jets. This contribution to the conference proceedings will review the application of innovative reconstruction techniques to supersymmetry searches in ATLAS.
On separate chemical freeze-outs of hadrons and light (anti)nuclei in high energy nuclear collisions
Authors: Bugaev K. A. , Grinyuk B. E. , Ivanytskyi A. I. , Sagun V. V. , Savchenko D. O. , Zinovjev G. M. , Nikonov E. G. , Bravina L. V. , Zabrodin E. E. , Blaschke D. B. , Kabana S. , Taranenko A. V.
Published: November 2019

The multiplicities of light (anti)nuclei were measured recently by the ALICE collaboration in Pb+Pb collisions at the center-of-mass collision energy

s

N
N

=
2.76

TeV

. Surprisingly, the hadron resonance gas model is able to perfectly describe their multiplicities under various assumptions. For instance, one can consider the (anti)nuclei with a vanishing hard-core radius (as the point-like particles) or with the hard-core radius of proton, but the fit quality is the same for these assumptions. In this paper we assume the hard-core radius of nuclei consisting of A baryons or antibaryons to follow the simple law

R
(
A
)
=

R
b

(
A
)

1
3

, where Rb
is the hard-core radius of nucleon. To implement such a relation into the hadron resonance gas model we employ the induced surface tension concept and analyze the hadronic and (anti)nuclei multiplicities measured by the ALICE collaboration. The hadron resonance gas model with the induced surface tension allows us to verify different scenarios of chemical freeze-out of (anti)nuclei. It is shown that the most successful description of hadrons can be achieved at the chemical freeze-out temperature Th
= 150 MeV, while the one for all (anti)nuclei is TA
= 168.5 MeV. Possible explanations of this high temperature of (anti)nuclei chemical freeze-out are discussed.
Beyond Standard Model searches by ATLAS and CMS
Authors: Erdmann Johannes
Published: November 2019

An overview of recent searches for physics beyond the Standard Model with the ATLAS and CMS experiments is given. The presented searches use data taken in 13 TeV proton-proton collisions at the LHC with an integrated luminosity of up to 80 fb−1.
Searches for electroweak production of higgsino with ATLAS
Authors: Todome Kazuki
Published: November 2019

Fine-tuning arguments suggest the mass of the supersymmetric partner of the Higgs boson, the Higgsino, is not too far from the weak scale. In most beyond standard model scenarios the Higgsinos are almost mass degenerate, and the search for Higgsinos represents an experimental challenge due to the near mass-degeneracy resulting in soft decay products, and the low production cross section. This proceeding presents recent ATLAS results of analyses explicitly targeting the Higgsino with a variety of experimental techniques.
Prospect for top quark FCNC searches at the FCC-hh
Authors: Mandrik Petr
Published: November 2019

FCC-hh is a proposed future energy-frontier hadron collider, which goal is to provide high luminosity proton collisions at a centre-of-mass energy of 100 TeV. The FCC-hh has an extremely rich physics program ranging from standard model (SM) measurements to direct searches for physics beyond the standard model (BSM). One of the processes sensitive to new physics is flavour-changing neutral currents (FCNC) that extremely rare in the SM but have enhanced behavior in several BSM scenarios. In this report we present results of projections of FCNC searches in top quark interactions to the FCC-hh conditions based on Monte-Carlo simulation of FCC-hh detector.
Searches for sterile neutrinos at very short baseline reactor experiments
Authors: Danilov M
Published: November 2019

For a long time there were 3 main experimental indications in favor of the existence of sterile neutrinos:

v
˜

e

appearance in the

v
˜

μ

beam in the LSND experiment,

v
˜

e

flux deficit in comparison with theoretical expectations in reactor experiments, and ve
deficit in calibration runs with radioactive sources in the Ga solar neutrino experiments SAGE and GALEX. All three problems can be explained by the existence of sterile neutrinos with the mass square difference in the ballpark of 1 eV2. Recently the MiniBooNE collaboration observed electron (anti)neutrino appearance in the muon (anti)neutrino beams. The significance of the effect reaches 6.0σ level when combined with the LSND result. Even more recently the NEUTRINO-4 collaboration claimed the observation of

v
˜

e

oscillations to sterile neutrinos with a significance slightly higher than 3σ. If these results are confirmed, New Physics beyond the Standard Model would be required. More than 10 experiments are devoted to searches of sterile neutrinos. Six very short baseline reactor experiments are taking data just now. We review the present results and perspectives of these experiments.
Reconstruction of the spectrum of cascades generated by VHE muons in the IceCube
Authors: Khokhlov Semyon
Published: November 2019

One of the best ways for the investigations of the VHE muons spectrum is measuring the spectrum of stochastic energy losses (cascades). IceCube is the detector capable of measuring the cascade spectrum in the energy region between tens of TeV and one PeV where manifestation of the prompt muon production mechanisms is predicted. In events with muon bundles, the longitudinal energy deposit profile reconstructed by means of a maximum likelihood method is analyzed. Cascade energies are estimated for the events in which the highest local energy deposit is much greater than the median energy deposit. The technique of cascade spectrum reconstruction has been tested with MC-simulated events. Criteria of the event selection, cascade parameters estimation accuracy and the efficiency of the spectrum reconstruction are discussed.
Analysis of thunderstorms based on the data obtained by MH URAGAN and DMRL-C
Authors: Kachur A P , Pavlyukov Yu B , Petrukhin A A , Serebryannik N I , Shutenko V V
Published: November 2019

Muon snapshots (muonographs) obtained by means of muon hodoscope URAGAN and meteorological maps from the Doppler weather radar DMRL-C during a thunderstorm event occurred in Moscow on August 30, 2018 are compared with each other in detail. Wavelet analysis of obtained muon data is performed. Search for possible predictors of a thunderstorm event is conducted.
Search for features in the cosmic-ray electron and positron spectrum measured by the Fermi Large Area Telescope
Authors: Mazziotta M. N.
Published: November 2019

Over its ten years of mission the Large Area Telescope onboard the Fermi Gamma-ray Space Telescope has collected the largest ever sample of high-energy cosmic-ray electron and positron events. Possible features in their energy spectrum could be a signature of the presence of nearby astrophysical sources or of more exotic sources, such as annihilation or decay of dark matter (DM) particles in the Galaxy. We will present the results of the search for possible delta-like line features in the cosmic-ray electron and positron spectrum. We will also present the results of the search for possible features originating from DM particles annihilating into electron-positron pairs. We are able to set constraints on DM masses up to 1.7TeV/c2 and exclude the thermal value of the relic annihilation cross section for DM candidates lighter than 150 GeV/c2.
Search for Hidden Photon Dark Matter Using a Multi-Cathode Counter
Authors: Kopylov A , Orekhov I , Petukhov V
Published: November 2019

A search for hidden-photon (HP) dark matter using a multi-cathode counter is reported. The technique based on counting of single electrons emitted from outer cathode of the proportional counter by hidden-photons was used. The apparatus and the calibration of the counter by ultraviolet lamp are described. It is shown that this technique attains a maximum sensitivity in the energy range of Vacuum Ultraviolet. From the results of measurements we set an upper limit on the photon-HP mixing parameter η. A further progress of using a multicathode technique is discussed.
Investigation of local deformations of muon flux angular distribution during CME with GSE-mapping technique
Authors: Astapov I I , Barbashina N S , Dmitrieva A N , Melnikova I A , Osetrova N V , Shutenko V V , Yashin I I
Published: November 2019

Coronal mass ejections (CME) have an impact on the flux of cosmic rays that penetrate the disturbed areas in the heliosphere and the near-terrestrial space. Unlike most ground-based cosmic ray detectors, the URAGAN muon hodoscope (MEPhI) allows to investigate both the integrated counting rate of registered particles and angular characteristics of the muon flux at the ground level. To select the local areas with statistically significant intensity changes, the angular distributions for the last hour and preceding it 24 hours corrected for the barometric effect are used. Angular distributions are smoothed, and the matrix of relative changes of the angular distribution in units of statistical errors is formed. The use of asymptotic directions calculated in advance, the angular cells of the matrix are mapped from the local coordinate system to the GSE coordinate system. The results of the study of GSE-mapping of local deformations of the angular distributions for different types of CMEs are discussed.
Reconstruction of particle’s energy spectrum in experiment with Unfolding technique
Authors: Alekseev V V , Bogomolov Yu V , Dunaeva O A , Mayorov A G , Malakhov V V , Rodenko S A
Published: November 2019

In elementary particle physics, the characteristics of the events can be distorted to varying degrees due to instrumental effects, which leads to inaccuracies in experimental distributions. To solve such difficulties and restore distributions close to the true, a various mathematical approaches are used. In this paper, we examine the quality of unfolding methods for solving this problem. Different variants of unfolding are tested for the quality of restoring the true distribution by simulating the passage of cosmic ray particles through the PAMELA magnetic spectrometer. The following algorithms were analyzed: D’Agostini, SVD and TUnfold.
Some manifestations of two-component dark matter structure in vectorlike hypercolor model
Authors: Bezuglov M , Beylin V , Kuksa V
Published: November 2019

In the framework of vectorlike hypercolor model with two generations it have been considered some peculiarities of diffuse gamma spectrum which is produced in the process of the Dark Matter annihilation. The model suggests two Dark Matter candidates and both of them contribute to this cross section depending on the model parameters. Masses of these DM components are estimated from analysis of kinetics of the DM and data on relic abundance.
Study of CP violation in the process of associated Higgs boson production with a decay into muon pair
Authors: Belyaev N , Konoplich R , Prokofiev K , Reese T
Published: November 2019

After the Higgs boson discovery at the LHC, a lot of additional measurements should be performed to understand in detail the properties of the observed particle. Searches for CP violation in different physics sectors are one of the most promising and important parts of these measurements. Associated Higgs boson production in pp collisions can be a powerful tool for searches for possible CP violation in the Higgs sector. In this paper, the study of CP sensitive observables constructed for a four lepton final state is presented. It is shown that azimuthal angle distributions of leptons in this process demonstrate a strong sensitivity to CP violation at the current limits on Higgs boson coupling parameters and can reveal a genuine mechanism of CP violation.
Weakly bound states of dtμ muonic molecular ion in quantum electrodynamics
Authors: Eskin A V , Korobov V I , Martynenko A P , Sorokin V V
Published: November 2019

The energy spectrum of ground and excited bound states of muonic molecule dtμ is calculated on the basis of stochastic variational method. The basis wave functions of the muonic molecule are taken in the Gaussian form. The matrix elements of the Hamiltonian are calculated analytically. For numerical calculation, a computer code is written in the MATLAB system. As a result, the numerical energy levels of ground and excited states of the muonic molecule dtμ are obtained.
Physical conditions in thin laminar-convective accretion flows
Authors: Malanchev Konstantin L. , Postnov Konstantin A. , Shakura Nikolay I.
Published: November 2019

The physical conditions of convection appearance in laminar accretion flows with microscopic transport coefficients are examined. Hot sparse ionised flow with periods below an hour found to be optically thin and have convective layer. Cold sparse molecular flow with period about a year found to be optically thin too and are fully convective. Ranges of temperature, density and period of optically thick laminar accretion flow are shown.
Studying method of microlensing effect estimation for a cluster of primordial black holes.
Authors: Toshchenko K A , Belotsky K M
Published: November 2019

Primordial black holes (PBH) attracted especially great attention last time. It is possible candidate not only to dark matter, but to supermassive black holes, gravitational waves events from black hole merger and others. However, recently there appeared constraints on PBH abundance from different observations. The given work is devoted to the model of PBH cluster in which some constraints can be avoided. We investigate effect of gravitation microlensing for PBH cluster. Analysis of respective data could alleviate limitations coming from them, but also could make it possible to test this model discriminating between the models of single and clustered PBHs.
Gravity theory tests with observations of stars near the black hole at the Galactic Center
Authors: Zakharov Alexander
Published: November 2019

One could say that 2018 is very special year since 55 years ago quasars were discovered, the Kerr solution has been found and the First Texas Symposium on Relativistic Astrophysics has been organized. In addition, 50 years ago, in 1968 the pulsar discovery paper has been published and the black hole concept has presented by J. A. Wheeler in his groundbreaking paper which was based on his report in December 1967. In last years remarkable achievements have been done in gravitational physics and related observations, in particular, gravitational waves and binary black holes with high stellar masses have been discovered, VLT, Keck and GRAVITY observe trajectories of bright stars and gas clouds near the Galactic Center (GC) with improving accuracy. It is clear that the Galactic Center (Sgr A*) is a specific place. Our Sun is located at a distance around 8 kpc from the Galactic Center (GC). Earlier, astronomers suggested a number of different including exotic ones such as boson stars, fermion balls, neutrino balls, a cluster of neutron stars. Some of these models are ruled out or significantly constrained with consequent observations. A supermassive black hole with mass around 4 × 106Mʘis the most realistic model for GC. Precision observations of bright stars near the Galactic Center and observations of bright structures near the black hole at the Galactic Center to reconstruct shadow structure around the black hole with current and future observational VLBI facilities such as the Event Horizon Telescope give opportunities to test alternative theories of gravity. In particular, we got a graviton mass constraint which is comparable and consistent with constraints obtained recently by the LIGO-Virgo collaboration. We consider opportunities to improve current graviton mass mass constraints with future observations of bright stars. Similarly, from an analysis of bright star trajectories one could constrain a tidal charge which was predicted by a gravity theory with an additional dimension.
The gravitational dynamics of the primordial black holes cluster
Authors: Khromykh Leonid A. , Kirillov Alexander A.
Published: November 2019

We consider the numerical simulation of the N-body problem related to the primordial black holes (PBHs) cluster. To study the dynamics of the system we use modified NBODY6++ code aimed at the simulation of globular star clusters. Some qualitative results describing the evolution of the system are discussed. It is shown that the cluster successfully survives to the redshift z ∼ 20 ÷ 40 (despite evaporation and coalescence of the PBHs). Starting from this moment an accretion begins to play significant role in speeding up the mass growth of the massive bodies.
On generalized Melvin solutions for Lie algebras of rank 3
Authors: Bolokhov S V , Ivashchuk V D
Published: November 2019

A multidimensional generalization of Melvin’s solution for an arbitrary simple Lie algebra G is considered. The gravitational model contains n 2-forms and l > n scalar fields, where n is the rank of G. The solution is governed by a set of n functions Hs
(z) obeying n ordinary differential equations with certain boundary conditions imposed. It was conjectured earlier that these functions should be polynomials (the so-called fluxbrane polynomials). The polynomials Hs
(z), s = 1,…, 6, corresponding to the Lie algebra E
6 are obtained. They depend upon integration constants Qs
, s = 1,…, 6 . The polynomials obey symmetry and duality identities. The latter ones are used in deriving asymptotic relations for solutions at large distances which are presented in the paper. The power-law asymptotic relations for E
6 - polynomials at large z are governed by integer-valued matrix v = A
−1 (I + P), where A
−1 is inverse Cartan matrix, I is identity matrix and P is permutation matrix, corresponding to a generator of the Z
2-group of symmetry of the Dynkin diagram. The 2-form fluxes Φ
s
are calculated, s = 1, …, 6.
Superheavy objects composed of nuclear and dark matter
Authors: Gani Vakhid A. , Khlopov Maxim Yu. , Voskresensky Dmitry N.
Published: November 2019

We consider a model of OHe atomic dark matter formed by Coulomb binding of the hypothetical stable double-charged massive O
– – particles with nuclei of primordial helium. Such a dark matter can be captured by ordinary matter forming superheavy nuclei. We propose a possibility of self-bound by nuclear and electromagnetic interaction O-nuclearites as well as more massive gravitating ones and discuss effect of accumulation of OHe atoms in stars and their effect in stellar evolution.
Bound orbits near black holes with scalar hair
Authors: Potashov I M , Tchemarina Ju V , Tsirulev A N
Published: November 2019

We consider spherically symmetric black holes with minimally coupled scalar fields and concentrate our attention on asymptotically flat self-gravitating configurations having the event horizons located at radii much smaller than 2m. We think of such configurations as rigorous mathematical models of the gravitating objects, surrounded by dark matter, in the centres of normal galaxies. It turns out that the radius of the event horizon of a scalar field black hole always less than the Schwarzschild radius of vacuum black hole of the same mass and can be arbitrary close to zero. In astronomical observations, a key role in distinguishing between black holes, wormholes, and naked singularities plays measuring parameters of bound quasiperiodic orbits, in particular, the shape of an orbit and the angle of precession of its pericentre. We consider a typical two-parameter family of compact scalar field black holes and compute numerically the shapes of some bound orbits. We find that a key feature of bound orbits around a compact black hole is that the angle between closest pericentre points is either negative or, at least, less than that for the Schwarzschild black hole of the same mass.
The AEgIS experiment: towards antimatter gravity measurements
Authors: Khalidova O , Aghion S , Amsler C , Antonello M , Belov A , Bonomi G , Brusa R S , Caccia M , Camper A , Caravita R , Castelli F , Cerchiari G , Comparat D , Consolati G , Demetrio A , Noto L D , Doser M , Evans C , Fani M , Ferragut R , Fesel J , Fontana A , Gerber S , Giammarchi M , Gligorova A , Guatieri F , Hackstock P , Haider S , Hinterberger A , Holmestad H , Kellerbauer A , Krasnický D , Lagomarsino V , Lansonneur P , Lebrun P , Malbrunot C , Mariazzi S , Marton J , Matveev V , Müller S , Nebbia G , Nedelec P , Oberthaler M , Pagano D , Penasa L , Petracek V , Prelz F , Prevedelli M , Rienaecker B , Robert J , Røhne O , Rotondi Alberto , Sandaker H , Santoro R , Smestad L , Sorrentino F , Testera G , Tietje I , Vujanovic M , Widmann E , Yzombard P , Zimmer C , Zmeskal J , Zurlo N
Published: November 2019

AE

g
¯

IS

(Antimatter Experiment: Gravity, Interferometry, Spectroscopy) is a CERN based experiment aiming to probe the Weak Equivalence Principle of General Relativity with antimatter by studying free fall of antihydrogen in the Earth’s gravitational field. A pulsed cold beam of antihydrogen produced by charge exchange between Rydberg positronium and cold antiprotons will be horizontally accelerated by an electric field gradient. The free fall of antihydrogen will then be measured by a classical moire deflectometer. An overview of the experimental setup, present status of the experiment along with current achievements and results is presented.
Measurement of the energy spectra and of the angular distribution of the Transition Radiation with a silicon strip detector
Authors: Loparco F , Alozy J , Belyaev N , Campbell M , Cherry M , Dachs F , Doronin S , Filippov K , Fusco P , Gargano F , Heijne E , Konovalov S , Krasnopevtsev D , Llopart X , Mascagna V , Mazziotta M N , Pernegger H , Ponomarenko D , Prest M , Pyatiizbyantseva D , Radomskii R , Rembser C , Romaniouk A , Savchenko A A , Schaefer D , Schioppa E J , Shchukin D , Sergeeva D Yu , Shulga E , Smirnov S , Smirnov Y , Soldani M , Spinelli P , Strikhanov M , Teterin P , Tikhomirov V , Tishchenko A A , Vallazza E , van Beuzekom M , van der Heijden B , Vorobev K , Zhukov K
Published: November 2019

We plan to develop an advanced Transition Radiation Detector (TRD) for hadron identification in the TeV momentum range, based on the simultaneous measurement of the energies and of the emission angles of the Transition Radiation (TR) X-rays with respect to the radiating particles. To study the feasibility of this project, we have carried out a beam test campaign at the CERN SPS facility with 20 GeV/c electrons and muons up to 300 GeV/c. To detect the TR X-rays and the radiating particles, we used a 300 μm thick double-sided silicon strip detector, with a strip readout pitch of 50 μm. A 2 m long helium pipe was placed between the radiators and the detector, in order to ensure adequate separation between the TR X-rays and the radiating particle on the detector plane and to limit the X-ray absorption before the detector. We measured the double-differential (in energy and angle) spectra of the TR emitted by several radiators. The results are in good agreement with the predictions obtained from the TR theory.
GEM detectors for the Upgrade of the CMS Muon Forward system
Authors: Mocellin Giovanni
Published: November 2019

The CMS experiment is one of the two general purpose experiments at the CERN LHC. During LHC Phase-2 starting from 2026, the instantaneous luminosity delivered to CMS will reach 5 × 1034 cm−2s−1, resulting in high particle fluxes that require the detector to be upgraded. The forward regions, corresponding to the endcaps of the detectors, will be most affected. In the muon endcap system, triple-GEM chambers will complement the existing Cathode Strip Chambers, leading to a better identification of the muon tracks and a reduction of the trigger rate due to the suppression of fake candidates. Additionally, the forward coverage will be extended.

GEM chambers are being built in production sites spread in 7 countries around the world for the first station of the muon endcaps. Each chamber has an area of approximately 1 m2. Thus, high requirements on the uniformity across the detector are needed and the GEM chambers undergo multiple quality control tests. In parallel with the production and testing of the chambers, 10 GEM chambers have been integrated in CMS and are currently under commissioning (slice test). Such a test is essential to prepare for the upcoming installation and integration.

This contribution gives an introduction to GEM chambers and presents some results of the performance tests, both for quality control and slice test.
4π semiconductor beta-spectrometer for measurement of 144Ce – 144Pr spectra
Authors: Bakhlanov S , Derbin A , Drachnev I , Kotina I , Lomskaia I , Muratova V , Pilipenko N , Semenov D , Unzhakov E
Published: November 2019

Precision measurements of beta-spectra have always been and are still playing an important role in several fundamental physical problems, predominantly in neutrino physics. Magnetic and electrostatic spectrometers possess the superior energy resolution, but at the same time such devices appear to be very complex and large-scale setups. Since the electron free path at 3 MeV (which is, basically, the maximum beta-transition energy for long-living isotopes) does not exceed 2 g/cm3, solid state scintillation and ionization detectors were effectively employed for detection of electron. In case of semiconductor detectors there is a significant probability of back-scattering from the detector surface that depends on the detector material. This issue could be overcome by constructing a beta-spectrometer with 4π geometry, fully covering the source and capable of detecting backscattered electrons. Here we present a technology allowing production of a beta-spectrometer based on silicon detectors and having 4π geometry. The spectrometer developed had been fitted with a 144Ce-144Pr radioactive source and has demonstrated capability of performing precision beta-spectrometry for this nuclides.
The Nuclotron-based Ion Collider Facility Project. The Physics Programme for the Multi-Purpose Detector
Authors: Geraksiev N.S.
Published: November 2019

The Nuclotron-based Ion Collider fAcility (NICA) is a new accelerator complex under construction at the Joint Institute for Nuclear Research (JINR), Dubna, Russia. The main goal of the planned facility is to provide accelerated particle beams for a wide range of experimental studies of the hot and dense strongly interacting QCD matter generated during collisions. The NICA project in its entirety allows for a fixed target experimental site, as well as two interaction points. The heavy ion programme includes two planned detectors: Baryonic Matter at Nuclotron (BM@N) - a fixed target experiment with extracted Nuclotron beams; and a collider-mode experiment at one of the interaction points - the MultiPurpose Detector (MPD). For the NICA collider, the accelerated beams by design will consist of particles ranging from protons and light nuclei to fully stripped gold ions. Beam energies will span

s

p
p

=
12
−
27

GeV

with luminosity Lpp
≥ 1 × 1030 cm−2s−1, and

s

A
u
A
u

=
4
−
11

GeV

, and average luminosity LAuAu
= 1 × 1027 cm−2s−1. The second interaction point is planned to be occupied by a third experiment - Spin Physics Detector (SPD), which will focus on the investigation of nucleon spin structure and polarization phenomena through the use of polarized proton and deuteron beams. A brief overview of the Multi-Purpose Detector is presented along with the major sub-detector systems. The MPD research programme will focus on multiple observables including collective flow, particle multiplicity and spectra. Special attention will be given to strangeness production and vector mesons, event-by-event fluctuations and hadron femtoscopy measurements. Several feasibility studies are referenced.
A U.S.-based Electron-Ion Collider
Authors: Guzey V
Published: November 2019

An Electron-Ion Collider (EIC) in USA is currently discussed as a next-generation facility for high-energy nuclear physics. The main goal of the EIC is to study fundamental questions of Quantum Chromodynamics, which include the origin of the nucleon mass and spin and the three-dimensional structure of the nucleon in terms of quarks and gluons, the emergent properties of dense systems of gluons, and influence of nuclear matter on distributions of quarks and gluons and propagation of color charges through it. The EIC machine designs are aimed at achieving variable center of mass energies of 20 – 100 GeV, upgradable to 150 GeV, high degree of polarization ( 70%) of beams of electrons, protons and light nuclei, high collision luminosity of 1033–34 cm–2s–1, and ion beams from deuteron to heaviest (Lead) nuclei. In this contribution, we present the current status of the EIC project, its physics program, and proposed designs of EIC realization.
The Carpet-3 multipurpose shower array for searching cosmic diffuse gamma rays with energy Eγ > 100 TeV
Authors: Kudzhaev A U , Dzhappuev D D , Afashokov Yu Z , Gorbacheva E A , Dzaparova I M , Khadzhiev M M , Klimenko N F , Kurenya A N , Lidvansky A S , Mikhailova O I , Ptitsyna K V , Petkov V B , Romanenko V S , Yanin A F
Published: November 2019

An experiment for measuring the flux of cosmic gamma rays with energy above 100 TeV is currently being prepared at the Baksan Neutrino Observatory of the Institute for Nuclear Research, Russian Academy of Sciences. At present the plastic scintillation counters with a total continuous area of 410 m2 are installed in the muon detector (MD) underground tunnels, and they are totally equipped with electronics. Six modules of shower detectors have been already placed on the surface of the MD absorber. In each of them 9 standard plastic scintillation counters are placed with an area of 1 m2 each. These modules are components of the ground surface part of Carpet-3 shower array. The data acquisition system for this array is almost ready. Expected flux limits for cosmic diffuse gamma rays of galactic origin in this work is close to existing experimental limits in the range lower than about 5 PeV, and with improved sensitivity of Carpet-3 one can hope to detect this flux or at least to obtain the best upper limit.
On application of wobbler in experiments with cylindrical targets
Authors: Suleymenov E M , Barminova H Y
Published: November 2019

For the experiments with irradiation of cylindrical targets by intense heavy ion beams which are actual for fundamental and applied researches (laboratory astrophysics, heavy ion inertial fusion, ion therapy, industry) it is necessary to shape the driver beam with hollow geometry. The wobbling method is of interest for such experiments. In the paper one of the problems of the method is considered leading to possible symmetry violation. The results of the simulation of the rotated beam dynamics are presented.
Neutron lifetime measurement with the big gravitational trap for ultracold neutrons. Current state and future prospects.
Authors: Serebrov A P , Kolomensky E A , Fomin A K , Krasnoschekova I A , Vassiljev A V , Prudnikov D V , Shoka I V , Chechkin A V , Chaikovskiy M E , Varlamov V E , Ivanov S N , Pirozhkov A N , Geltenbort P , Zimmer O , Jenke T , Van der Grinten M , Tucker M
Published: November 2019

A new measurement of the neutron lifetime, carried out with the aid of a large gravitational spectrometer made in Petersburg Institute of Nuclear Physics (PNPI) is presented: τn = 881.5 ± 0.7 ± 0.6 s. In our experiment the measurement of neutron lifetime is carried out using the method of storing ultracold neutrons in a material trap with gravitational barrier. Further improvement of the obtained result can be achieved at the helium temperatures. Here we present our neutron lifetime result, modified installation scheme and the first results of cryogenic tests are discussed.
Species kinetics in Ar-S2 plasma of the pulsed periodic discharge
Authors: Avtaeva S V
Published: November 2019

The kinetic (0D) model a longitudinal pulsed-periodic discharge in mixtures of sulfur vapor with argon based on solution of the balance equations for plasma species and an equation of the electron energy balance was developed and evolution of species densities was calculated in the discharge at pressure ~ 40 Torr. Radiation spectrum of the discharge is similar to solar spectrum in the wavelength range of 280–600 nm. The discharge plasma is electronegative; a discharge with electropositive plasma is non-stable and can exist during short time in a pulsed mode. As simulation shown densities of all charged and excited species fast increase during 1–1.5 μs after voltage pulse beginning, reach maximal values and then decrease because of diminishing electrons mean energy and density in decreasing field. It is found that density of S2
*(B
3Σ) molecules fast rises during voltage pulse and exceeds densities of other excited species; however when a pulse voltage decreases the density of S2
*(B
3Σ) molecules fast falls while density of resonance excited argon atoms decreases slower. This is the reason for appearance of strong Ar lines together with S2 bands in spectra of the longitudinal pulsed-periodic discharge in argon/sulfur vapor mixtures.
Monte-Carlo simulation of the ionization processes for discharges in the left branch of the Paschen curve
Authors: Grishkov A A , Korolev Yu D , Shklyaev V A
Published: November 2019

The paper deals with the development of the simulation methods applied to the low-pressure discharges in which the reduced electric field E/p is extremely high and there exists a problem for the correct description of the ionization processes in the classical electron avalanches. Here we use the PIC/MC code xoopic for calculation of the impact ionization coefficient α, the electron drift velocity and the electron diffusion coefficient D in the electron avalanches in nitrogen. The range of calculations covers the ratio E/p ≤ 1000 V·(cm·Torr)−1. The simulation method was tested on a simple analytical model of an electron avalanche and showed good agreement in low and moderate E/p. It is shown that in conditions of high E/p the spatial distribution of electrons in the avalanche head based on the concepts of electron mobility during their drift motion and diffusion coefficient is not quite correct. The work confirmed that at the very low pressures pre-breakdown phenomena and the transition to the next stage of high-current breakdown cannot be based on ideas about classical electron avalanches.
Phenomena at the electrode surfaces and localization of the volume discharges in small-sized sealed-off TEA-CO2 lasers
Authors: Kozlov B A , Mai T N
Published: November 2019

The mechanism of localization of volume discharge and limitation of resource in small-sized sealed-off TEA-CO2 lasers are grounded. The main processes which initiate the transition of volume discharge into the local one are connected with autoemissive currents from microinhomogeneities at the cathode surfaces. Maximal resource achieved in TEA-CO2 lasers with electrodes made from materials which more stable to the influence of the volume discharge plasma. There are Mo, Ti, Ta, Nb, W and C (graphite). Lifetime of the small-sized sealed-off TEA-CO2 laser up to 2000 hours using graphite cathodes has been achieved.
High-voltage pulse generators for effective pumping of super-atmospheric pressure CO2-lasers
Authors: Kozlov B A , Makhanko D S , Seredinov V I , Pyanchenkov S A
Published: November 2019

This work is devoted to describing of constructions and main characteristics of some types compact pulse generators with amplitude of voltage pulses up to 200 kV, rise-times about 10 ns and pulse energy per pulse up to 20 J. For reduction of rise-time of high-voltage pulses were used spark-discharge two electrodes commutators (sharpeners) at working pressures up to 100 atm.
Optical and kinetic characteristics of a pulsed discharge in argon with aluminum vapor at atmospheric pressure
Authors: Kurbanismailov V S , Maiorov S A , Ragimkhanov G B , Khalikova Z R
Published: November 2019

Experimental studies of the space-time dynamics of the formation and spectra of optical radiation of a pulsed discharge in argon in external electric and magnetic fields were performed. It was shown that during the formation of a pulsed discharge in argon in the process of diffuse luminescence propagation, cathode spots form on the cathode on it, as evidenced by the presence of lines of electrode material vapor in the plasma emission spectrum. Monte Carlo methods are used to study the kinetic characteristics of the drift of aluminum ions in argon.
Investigation of electron transition into runaway mode in inhomogeneous electric field in various gas media
Authors: Mamontov Yu I , Lisenkov V V , Uimanov I V
Published: November 2019

Transition of field-emitted electrons into the runaway mode is investigated in the region of enhanced electric field determined by the configuration of a microtip on a cathode for various gas media composition and pressure. The research is done using simulation of electron motion in the inhomogeneous electric field with a help of the Monte-Carlo procedure in the 3D configuration. Calculations were carried out for Nitrogen, Hydrogen and CO2:N2:He mixture (1:1:3). It’s shown that passage through a relatively small region of the enhanced field in the vicinity of the micro-spike may substantially facilitate electron transition to the runaway mode. This effect enhances at pressures of greater than 10 atm. In our opinion, the resulting runaway electrons may provide pre-ionization of gas medium and formation of the initial stage of a volume discharge. The results obtained are of interest for studies of the switching properties of ultrahigh pressure gaps and the use of a volume discharge for lasers pumping.
Investigation of plasma ion composition generated by high-power impulse magnetron sputtering (HiPIMS) of graphite
Authors: Oskomov K V , Vizir A V
Published: November 2019

High-power impulse magnetron sputtering (HiPIMS) of graphite is used to increase the density of the plasma (up to 1013 cm−3) and the fraction of ionization of carbon (up to 70 %). It makes possible to increase the ion bombardment of the growing film by applying a negative high-frequency (HF) bias potential to the substrate, which allows deposition of diamond-like (DLC) coatings obtained by subplantation mechanism. The purpose of this research was to measure the ion composition of plasma during HiPIMS of graphite by time-of-flight spectrometer depending on discharge parameters (current, pressure, pulse-width). For any pulse-width (up to 250 μs) increase of discharge current leaded to growth of C+ fraction (up to 60 % for 70 A) that results from more intense sputtering of the graphite cathode. Decrease of argon pressure down to 3×10−4 Torr leaded to reduction of C+ fraction down to 13 %, which is related to less intense sputtering. It can be seen that as the argon pressure in the vacuum chamber increases, the percentage of carbon ions in the flow increases (up to 75 %), which may due to the “cooling” of electrons with increasing pressure - they no longer have enough energy to ionize argon (15 eV), but enough energy to ionize carbon (3.6 eV). Thus, using of time-of-flight analyzing of plasma ion composition generated by HiPIMS of graphite one can choose optimum discharge pressure and current – both of them should be maximized.
Probe diagnostics of the plasma plume created by a magnetic nozzle of an inductively coupled plasma source
Authors: Shumeiko A I , Telekh V D
Published: November 2019

The Air-Breathing Helicon Plasma Thruster, a thruster utilizing ambient air which is suggested to support small spacecraft on very low Earth’s orbits, has been tested successfully. Using a retarding field energy analyser and Langmuir probe, the specific impulse have been confirmed for operating conditions of 1.5 mg·s−1 of air, 50 mPa gas pressure, 120 W of radio-frequency forward power at 13.56 MHz, and a maximum axial magnetic field of 200 G at the 200 km attitude. The inductively coupled plasma and ion beam formed have been characterized axially, and the measured beam velocity is about 1100 km·s−1 for these conditions.
Holographic interferometry for the study of an electric explosion of titanium wires
Authors: Skryabin A S , Pavlov A V , Kartova A M , Telekh V D
Published: November 2019

The paper presents the results of a slow (with a characteristic process time τ ≈ 50–100 μs) electric explosion (in an air medium) of thin (with a characteristic diameter δ ≈ 20–50 μm) titanium wires with holographic interferometry. A characteristic energy input into the wires was varied from 2.5 to 3.0 J·mg−1. The optical scheme of interferometry laser diagnostics was discussed. The formation of the main explosion features (shock front, explosion products, etc.) was registered. An interference shift allowed calculating of changing of a refractive index and a density in different zones of the explosion. The simplest estimations indicated that a density in shock compressed gas was varied from 1.1×1020 to 2.4×1020 cm−3.
Generation of direct and reverse runaway electron beams in atmospheric air using anodes made of different metals
Authors: Tarasenko V F , Baksht E Kh , Rybka D V , Sorokin D A , Kozyrev A V , Kozhevnikov V Yu
Published: November 2019

This study presents results on the generation of runaway electron beams propagating from the cathode in both directions: towards the anode and in the opposite direction. The investigations were carried out in atmospheric air excited by nanosecond voltage pulses of both polarities. In the experiments, anodes made of aluminum, brass, and tantalum were used. It was shown that the amplitude of the current pulse of an electron beam generated in the direction opposite to the anode depends on the atomic number of the metal from which the anode is made. At the same time, it is important to note that for a beam generated in the direction of the anode, such dependence was not observed.