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L. I. Sarycheva

Publications and source records attributed to L. I. Sarycheva.

At least 19 recordsLinked to original sources
arXiv2011

The CMS Magnetic Field Map Performance

The Compact Muon Solenoid (CMS) is a general-purpose detector designed to run at the highest luminosity at the CERN Large Hadron Collider (LHC). Its distinctive featuresinclude a 4 T superconducting solenoid with 6 m diameter by 12.5 m long free bore, enclosed inside a 10000-ton return yoke made of construction steel. Accurate characterization of the magnetic field everywhere in the CMS detector is required. During two major tests of the CMS magnet the magnetic flux density was measured inside the coil in a cylinder of 3.448 m diameter and 7 m length with a specially designed field-mapping pneumatic machine as well as in 140 discrete regions of the CMS yoke with NMR probes, 3-D Hall sensors and flux-loops. A TOSCA 3-D model of the CMS magnet has been developed to describe the magnetic field everywhere outside the tracking volume measured with the field-mapping machine. A volume based representation of the magnetic field is used to provide the CMS simulation and reconstruction software with the magnetic field values. The value of the field at a given point of a volume is obtained by interpolation from a regular grid of values resulting from a TOSCA calculation or, when available, from a parameterization. The results of the measurements and calculations are presented, compared and discussed.

physics.ins-det↗
arXiv2009

Estimates of hadron azimuthal anisotropy from multiparton interactions in proton-proton collisions at sqrt(s) = 14 TeV

We estimate the amount of collective "elliptic flow" expected at mid-rapidity in proton-proton (p-p) collisions at the CERN Large Hadron Collider (LHC), assuming that any possible azimuthal anisotropy of the produced hadrons with respect to the plane of the reaction follows the same overlap-eccentricity and particle-density scalings as found in high-energy heavy ion collisions. Using a Glauber eikonal model, we compute the p-p eccentricities, transverse areas and particle-multiplicities for various phenomenological parametrisations of the proton spatial density. For realistic proton transverse profiles, we find integrated elliptic flow v2 parameters below 3% in p-p collisions at sqrt(s) = 14 TeV.

hep-ph↗
arXiv2007

Two-dimensional discrete wavelet analysis of multiparticle event topology in heavy ion collisions

The event-by-event analysis of multiparticle production in high energy hadron and nuclei collisions can be performed using the discrete wavelet transformation. The ring-like and jet-like structures in two-dimensional angular histograms are well extracted by wavelet analysis. For the first time the method is applied to the jet-like events with background simulated by event generators, which are developed to describe nucleus-nucleus collisions at LHC energies. The jet positions are located quite well by the discrete wavelet transformation of angular particle distribution even in presence of strong background.

nucl-ex↗
arXiv2007

Confirmation of a pi_1^0 Exotic Meson in the ηπ^0 System

The exclusive reaction $π^- p \to ηπ^0 n$, $η\to π^+ π^- π^0$ at 18 GeV$/c$ has been studied with a partial wave analysis on a sample of 23~492 $ηπ^0 n$ events from BNL experiment E852. A mass-dependent fit is consistent with a resonant hypothesis for the $P_+$ wave, thus providing evidence for a neutral exotic meson with $J^{PC} = 1^{-+}$, a mass of $1257 \pm 20 \pm 25$ MeV$/c^2$, and a width of $354 \pm 64 \pm 60$ MeV$/c^2$. New interpretations of the meson exotics in neutral $ηπ^0$ system observed in E852 and Crystal Barrel experiments are discussed.

hep-ex↗
arXiv2006

Rapidity-dependence of jet shape broadening and quenching

The jet shape modification due to partonic energy loss in the dense QCD matter is investigated by the help of the special transverse energy-energy correlator in the vicinity of maximum energy deposition of every event. In the accepted scenario with scattering of jet hard partons off comoving medium constituents this correlator is independent of the pseudorapidity position of a jet axis and becomes considerably broader (symmetrically over the pseudorapidity and the azimuthal angle) in comparison with $pp$-collisions. At scattering off "slow" medium constituents the broadening of correlation functions is dependent on the pseudorapidity position of a jet axis and increases noticeably in comparison with the previous scenario for jets with large enough pseudorapidities. These two considered scenarios result also in the different dependence of jet quenching on the pseudorapidity.

hep-ph↗
arXiv2005

High energy Cherenkov gluons at RHIC and LHC

The collective effect of emission by the forward moving partons of high energy Cherenkov gluons in nucleus-nucleus collisions at RHIC and LHC energies is considered. It can reveal itself as peaks in the pseudorapidity distribution of jets at midrapidities or as a ring-like structure of individual events in event-by-event analysis. The pseudorapidity distribution of centers of dense isolated groups of particles in HIJING model is determined. It can be considered as the background for Cherenkov gluons. If peaks above this background were found in experiment, they would indicate new collective effects.

nucl-ex↗
arXiv2005

The background for Cherenkov gluons at RHIC and LHC energies

The pseudorapidity distribution of centers of dense isolated groups of particles in HIJING model is determined. It can be considered as the background for Cherenkov gluons. If peaks over this background were found in experiment, they would indicate the onset of new collective effects.

hep-ph↗
arXiv2005

Jet activity versus alignment

The hypothesis about the relation between the observed alignment of spots in the x-ray film in cosmic ray emulsion experiments and the features of events in which jets prevail at super high energies is tested. Due to strong dynamical correlation between jet axis directions and that between momenta of jet particles (almost collinearity), the evaluated degree of alignment is considerably larger than that for randomly selected chaoticly located spots in the x-ray film. It appears comparable with experimental data provided that the height of primary interaction, the collision energy and the total energy of selected clusters meet certain conditions. The Monte Carlo generator PYTHIA, which basically well describes jet events in hadron-hadron interactions, was used for the analysis.

hep-ph↗
arXiv2004

Medium-modified fragmentation of b-jets tagged by a leading muon in ultrarelativistic heavy ion collisions

The possibility to observe the medium-modified fragmentation of hard b-quarks tagged by a leading muon in ultrarelativistic heavy ion collisions is analyzed. We have found that reasonable statistics, ~20000 events per 1 month of LHC run with lead beams, can be expected for the realistic geometrical acceptance and kinematic cuts. The numerical estimates on the effect of the medium-induced softening b-jet fragmentation function are given.

hep-ph↗
arXiv2004

Calorimetric transverse energy-energy correlations as a probe of jet quenching

The sensitivity of calorimetric energy-energy correlation function to the medium-induced energy loss of fast partons in high multiplicity heavy ion interactions is demonstrated at the appropriate selection of events for the analysis, namely, the availability of one high-pt jet in an event at least and using the procedure of ``thermal'' background subtraction. Without jet trigger this correlation function manifests the global structure of transverse energy flux: the correlator is isotropic for central collisions, and for non-central collisions it is sensitive to the azimuthal anisotropy of energy flow reproducing its Fourier harmonics but with the coefficients squared.

hep-ph↗
arXiv2003

A Study of the ηπ^{0} Spectrum and Search for a J^{PC} = 1^{-+} Exotic Meson

A partial wave analysis (PWA) of the of the $ηπ^0$ system (where $η\to γγ$) produced in the charge exchange reaction $π^-p\to ηπ^0n$ at an incident momentum of 18 GeV$/c$ is presented as a function of ${ηπ^0}$ invariant mass, $m_{ηπ^0}$, and momentum transfer squared, $t_{π^{-}\toηπ}$, from the incident $π^-$ to the outgoing ${ηπ^0}$ system. $S$, $P$ and $D$ waves were included in the PWA. The $a_0(980)$ and $a_2(1320)$ states are clearly observed in the overall ${ηπ^0}$ effective mass distribution as well as in the amplitudes associated with $S$ wave and $D$ waves respectively after partial wave decomposition. The observed distributions in moments (averages of spherical harmonics) were compared to the results from the PWA and the two are consistent. The distribution in $t_{π^{-}\toηπ}$ for individual $D$ waves associated with natural and unnatural parity exchange in the $t$-channel are consistent with Regge phenomenology. Of particular interest in this study is the $P$ wave since this leads to an exotic $J^{PC}=1^{-+}$ for the $ηπ$ system. A $P$ wave is present in the data, however attempts to describe the mass dependence of the amplitude and phase motion with respect to the $D$ wave as a Breit-Wigner resonance are problematic. This has implications regarding the existence of a reported exotic $J^{PC} = 1^{-+}$ meson decaying into $ηπ^0$ with a mass near 1.4 GeV$/c^2$.

hep-ex↗
arXiv2003

Extracting the jet azimuthal anisotropy from higher order cumulants

We analyze the method for calculation of a coefficient of jet azimuthal anisotropy without reconstruction of the nuclear reaction plane considering the higher order correlators between the azimuthal position of jet axis and the angles of particles not incorporated in the jet. The reliability of this technique in the real physical situation under LHC conditions is illustrated.

hep-ph↗
arXiv2002

A method for analysing the jet azimuthal anisotropy in ultrarelativistic heavy ion collisions

The azimuthal anisotropy of jet spectra due to energy loss of jet partons in azimuthally non-symmetric volume of dense quark-gluon matter is considered for semi-central nuclear interactions at collider energies. We develop the techniques for event-by-event analysing the jet azimuthal anisotropy using particle and energy elliptic flow, and suggest a method for calculation of coefficient of jet azimuthal anisotropy without reconstruction of nuclear reaction plane.

hep-ph↗
arXiv2001

Azimuthal anisotropy of jet quenching at LHC

We analyze the azimuthal anisotropy of jet spectra due to energy loss of hard partons in quark-gluon plasma, created initially in nuclear overlap zone in collisions with non-zero impact parameter. The calculations are performed for semi-central Pb-Pb collisions at LHC energy.

hep-ph↗
arXiv2000

Inclusive meson production in peripheral collisions of ultrarelativistic heavy ions

There exist several proposals to use Weizsäcker-Williams photons generated by ultrarelativistic heavy ions to produce exotic particles in $γγ$ fusion reactions. To estimate the background conditions for such reactions we analyze various mechanisms of meson production in very peripheral collisions of ultrarelativistic heavy ions at RHIC and LHC energies. Besides $γγ$ fusion they include also electromagnetic $γA$ interactions and strong nucleon-nucleon interactions in grazing $AA$ collisions. All these processes are characterised by low multiplicities of produced particles. $γA$ and $AA$ events are simulated by corresponding Monte Carlo codes, RELDIS and FRITIOF. In each of these processes a certain fraction of pions is produced close to the mid-rapidity region that gives a background for the $γγ$ events. The possibility of selecting mesons produced in $γγ$ fusion events via different $p_t$ cut procedures is demonstrated.

nucl-th↗
arXiv1999

Monojet rates in ultrarelativistic heavy ion collisions

Basing on model concepts we research the monojet-to-dijet ratio as a function of the jet energy detection threshold in ultrarelativistic collisions of nuclei. We provide an comparative analysis of the contribution to monojet yield from gluon radiation before initial hard parton-parton scattering and from non-symmetric dijet energy losses in quark-gluon plasma, which expected to be created in ultrarelativistic heavy ion collisions.

hep-ph↗