566 research outputs found
Multiplicity Dependence of Non-extensive Parameters for Strange and Multi-Strange Particles in Proton-Proton Collisions at TeV at the LHC
The transverse momentum () spectra in proton-proton collisions at
= 7 TeV, measured by the ALICE experiment at the LHC are analyzed
with a thermodynamically consistent Tsallis distribution. The information about
the freeze-out surface in terms of freeze-out volume, temperature and the
non-extenisivity parameter, , for , ,
and are extracted by
fitting the spectra with Tsallis distribution function. The
freeze-out parameters of these particles are studied as a function of charged
particle multiplicity density (). In addition, we also study
these parameters as a function of particle mass to see any possible mass
ordering. The strange and multi-strange particles show mass ordering in volume,
temperature, non-extensive parameter and also a strong dependence on
multiplicity classes. It is observed that with increase in particle
multiplicity, the non-extensivity parameter, decreases, which indicates the
tendency of the produced system towards thermodynamic equilibration. The
increase in strange particle multiplicity is observed to be due to the increase
of temperature and not to the size of the freeze-out volume.Comment: Version similar to the published version in EPJ
Transverse Momentum Spectra and Nuclear Modification Factor using Boltzmann Transport Equation with Flow in Pb+Pb collisions at = 2.76 TeV
In the continuation of our previous work, the transverse momentum ()
spectra and nuclear modification factor () are derived using relaxation
time approximation of Boltzmann Transport Equation (BTE). The initial
-distribution used to describe collisions has been studied with the
pQCD inspired power-law distribution, the Hagedorn's empirical formula and with
the Tsallis non-extensive statistical distribution. The non-extensive Tsallis
distribution is observed to describe the complete range of the transverse
momentum spectra. The Boltzmann-Gibbs Blast Wave (BGBW) distribution is used as
the equilibrium distribution in the present formalism, to describe the
-distribution and nuclear modification factor in nucleus-nucleus
collisions. The experimental data for Pb+Pb collisions at =
2.76 TeV at the Large Hadron Collider at CERN have been analyzed for pions,
kaons, protons, and . It is observed that the present formalism
while explaining the transverse momentum spectra upto 5 GeV/c, explains the
nuclear modification factor very well upto 8 GeV/c in for all these
particles except for protons. is found to be independent of the degree
of non-extensivity, after 8 GeV/c.Comment: Same as published version in EPJ
Radial Flow in Non-Extensive Thermodynamics and Study of Particle Spectra at LHC in the Limit of Small
We expand the Tsallis distribution in a Taylor series of powers of (q-1),
where q is the Tsallis parameter, assuming q is very close to 1. This helps in
studying the degree of deviation of transverse momentum spectra and other
thermodynamic quantities from a thermalized Boltzmann distribution. After
checking thermodynamic consistency, we provide analytical results for the
Tsallis distribution in the presence of collective flow up to the first order
of (q-1). The formulae are compared with the experimental data.Comment: Replaced with Accepted version in Eur. Phys. J.
Radial Flow and Differential Freeze-out in Proton-Proton Collisions at TeV at the LHC
We analyse the transverse momentum ()-spectra as a function of
charged-particle multiplicity at midrapidity () for various
identified particles such as , , , ,
, , and + in
proton-proton collisions at = 7 TeV using Boltzmann-Gibbs Blast Wave
(BGBW) model and thermodynamically consistent Tsallis distribution function. We
obtain the multiplicity dependent kinetic freeze-out temperature () and radial flow () of various particles after fitting the -distribution with BGBW model. Here, exhibits mild dependence
on multiplicity class while shows almost independent behaviour. The
information regarding Tsallis temperature and the non-extensivity parameter
() are drawn by fitting the -spectra with Tsallis distribution
function. The extracted parameters of these particles are studied as a function
of charged particle multiplicity density (). In addition to
this, we also study these parameters as a function of particle mass to observe
any possible mass ordering. All the identified hadrons show a mass ordering in
temperature, non-extensive parameter and also a strong dependence on
multiplicity classes, except the lighter particles. It is observed that as the
particle multiplicity increases, the -parameter approaches to
Boltzmann-Gibbs value, hence a conclusion can be drawn that system tends to
thermal equilibrium. The observations are consistent with a differential
freeze-out scenario of the produced particles.Comment: Published versio
Evolution of strange and multi-strange hadron production with relative transverse multiplicity activity in underlying event
In this work, relative Underlying Event (UE) transverse multiplicity activity
classifier () is used to study the strange and multi-strange
hadron production in proton-proton collisions. Our study with
would allow to disentangle these particles which are originating from the soft
and hard QCD processes. We have used the PYTHIA 8 MC with different
implementation of color reconnection and rope hydronisation models to
demonstrate the proton-proton collisions data at = 13 TeV. The
relative production of strange and multi-strange hadrons are discussed
extensively in low and high transverse activity region. In this contribution,
the relative strange hadron production is enhanced with increasing . This enhancement is significant for strange baryons as compared to
mesons. In addition, the particle ratios as a function of
confirms the baryon enhancement in newCR, whereas Rope model confirms the
baryon enhancement only with strange quark content. An experimental
confirmation of such results will provide more insight into the soft physics in
the transverse region which will be useful to investigate various tunes based
on hadronization and color reconnection schemes
Effect of Hagedorn States on Isothermal Compressibility of Hadronic Matter formed in Heavy-Ion Collisions: From NICA to LHC Energies
In this work, we have studied the isothermal compressibility () as
a function of temperature, baryon chemical potential and centre-of-mass energy
() using hadron resonance gas (HRG) and excluded-volume hadron
resonance gas (EV-HRG) models. A mass cut-off dependence of isothermal
compressibility has been studied for a physical resonance gas. Further, we
study the effect of heavier resonances ( 2 GeV) on the isothermal
compressibility by considering the Hagedorn mass spectrum,
. Here, the parameters, and
are extracted after comparing the results of recent lattice QCD
simulations at finite baryonic chemical potential. We find a significant
difference between the results obtained in EV-HRG and HRG models at a higher
temperatures and higher baryochemical potentials. The inclusion of the Hagedorn
mass spectrum in the partition function for hadron gas has a large effect at a
higher temperature. A higher mass cut-off in the Hagedorn mass spectrum takes
the isothermal compressibility to a minimum value, which occurs near the
Hagedorn temperature (). We show explicitly that at the future low energy
accelerator facilities like FAIR (CBM), Darmstadt and NICA, Dubna the created
matter would be incompressible compared to the high energy facilities like RHIC
and LHC.Comment: Same as published pape
Bose-Einstein condensation of triplons in the S=1 tetramer antiferromagnet K2Ni2(MoO4)3: A compound close to quantum critical point
The structure of K2Ni2(MoO4)3 consists of S=1 tetramers formed by Ni^{2+}
ions. The magnetic susceptibility chi(T) and specific heat Cp(T) data on a
single crystal show a broad maximum due to the low-dimensionality of the system
with short-range spin correlations. A sharp peak is seen in chi(T) and Cp(T) at
about 1.13 K, well below the broad maximum. This is an indication of magnetic
long-range order i.e., the absence of spin-gap in the ground state.
Interestingly, the application of a small magnetic field (H>0.1 T) induces
magnetic behavior akin to Bose-Einstein condensation (BEC) of triplon
excitations observed in some spin-gap materials. Our results demonstrate that
the temperature-field (T-H) phase boundary follows a power-law
(T-T_{N})propotional to H^(1/alpha) with the exponent 1/alpha close to 2/3, as
predicted for BEC scenario. The observation of BEC of triplon excitations in
small H infers that K2Ni2(MoO4)3 is located in the proximity of a quantum
critical point, which separates the magnetically ordered and spin-gap regions
of the phase diagram.Comment: 5 pages, 5 figures, Accepted in Phys. Rev. B Rapid Communication
Latest results on the production of hadronic resonances in ALICE at the LHC
Measurement of short-lived hadronic resonances are used to study different aspects of particle production and collision dynamics in pp, p–A and relativistic heavy-ion collisions. The yields of resonances are sensitive to the competing processes of hadron rescattering and regeneration, thus making these particles unique probes of the properties of the late hadronic phase. Measurements of resonances with different masses and quantum numbers also provide insight into strangeness production and processes that determine the shapes of particle momentum spectra at intermediate transverse momenta, as well as the species dependence of hadron suppression at high momentum. We present the comprehensive set of results in the ALICE experiment with unprecedented precision for ρ(770)0, K∗(892), φ(1020), Σ(1385)±, Λ(1520), and Ξ(1530)0 production in pp, p–Pb, Xe–Xe and Pb–Pb collisions in the energy range √sNN = 2.76-13 TeV, including the latest measurements from LHC Run 2. The obtained results are used to study the system-size and collision-energy evolution of transverse momentum spectra, particle ratios and nuclear modification factors and to search for the onset of collectivity in small collision systems. We compare these results to lower energy measurements and model calculations where available.publishedVersio
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