Journals
2018 EN
M. M. Aggarwal · Z. Ahammed · S. Aiola
+177 more
A large Time Projection Chamber is the main device for tracking andcharged-particle identification in the ALICE experiment at the CERN LHC. Afterthe second long shutdown in 2019/20, the LHC will deliver Pb beams colliding atan interaction rate of about 50 kHz, which is about a factor of 50 above thepresent readout rate of the TPC. This will result in a significant improvementon the sensitivity to rare probes that are considered key observables tocharacterize the QCD matter created in such collisions. In order to make fulluse of this luminosity, the currently used gated Multi-Wire ProportionalChambers will be replaced. The upgrade relies on continuously operated readoutdetectors employing Gas Electron Multiplier technology to retain theperformance in terms of particle identification via the measurement of thespecific energy loss by ionization d$E$/d$x$. A full-size readout chamberprototype was assembled in 2014 featuring a stack of four GEM foils as anamplification stage. The performance of the prototype was evaluated in a testbeam campaign at the CERN PS. The d$E$/d$x$ resolution complies with both theperformance of the currently operated MWPC-based readout chambers and thechallenging requirements of the ALICE TPC upgrade program. Detailed simulationsof the readout system are able to reproduce the data.
Journals
2018 EN
ZengKui Guo · Bhavani S. Sahu · Rongjun He
+8 more
TLQP-21 is a multifunctional neuropeptide and a promising new medicinal target for cardiometabolic and neurological diseases. However, to date its clearance kinetics and plasma stability have not been studied. The presence of four arginine residues led us to hypothesize that its half-life is relatively short. Conversely, its biological activities led us to hypothesize that the peptide is still taken up by adipose tissues effectively. [ 125 I]TLQP-21 was i.v. administered in rats followed by chasing the plasma radioactivity and assessing tissue uptake. Plasma stability was measured using LC-MS. In vivo lipolysis was assessed by the palmitate rate of appearance.
Journals
2018 EN
S. K. Tripathy · M. Younus · Z. Naik
+1 more
We have implemented spherical harmonics in default Wood Saxon distribution ofthe HIJING model and calculated various physical observables such as transversemomentum, charged particle multiplicity, nuclear modification factor andparticle ratios for charged particles at top RHIC energy with collisions ofUranium (U) nuclei. Results have been compared with available experimentaldata. We observe that, a particular type of collision configuration can producesignificant magnitude change in observables. We have noticed that the tip-tipconfiguration shows higher magnitude of particle yield in central collisions,while the body-body configuration shows higher value in the cases of peripheralcollisions, with the flip in the trend occurring for the mid-central U+Ucollisions. We observe that particle ratios are independent of configurationtype.
Journals
2018 EN
Nimmala Narendra · Nirakar Sahoo · Narendra Sahu
We propose a minimal extension of the standard model with U(1)_{B-L} \timesZ_{2} symmetry. In this model by assuming that the neutrinos are Dirac (i.e.$B-L$ is an exact symmetry), we found a simultaneous solution for non zeroneutrino masses and dark matter content of the universe. The observed baryonasymmetry of the universe is also explained using Dirac Leptogenesis, which isassisted by a dark sector, gauged under a U(1)_D symmetry. The latter symmetryof the dark sector is broken at a TeV scale and thereby giving mass to aneutral gauge boson Z_D. The standard model Z-boson mixes with the gauge bosonZ_D at one loop level and thus paves a way to detect the dark matter throughspin independent elastic scattering at terrestrial laboratories.
Journals
2018 EN
Debashis Das · Saswata Sahu · Dwipesh Majumder
We have studied the collective excitation of fractional quantum Hall effect(FQHE) in the rotating Bose-Einstein condensate (BEC) using CF theory at thefilling fraction $\nu=1/2$. The roton type of excitation in the FQHE ofelectron system is established over the years for all the filling fraction,whereas the collective excitation at $\nu=1/2$ filling fraction in the rotatingBEC shows no roton minimum. We have investigated this using composite fermiontheory with the P$\ddot{o}$schl-Teller interaction potential between theparticles. We have seen that the long range interaction will give the roton,whereas short range interaction gives no roton minimum.
Journals
2018 EN
STAR Collaboration · L. Adamczyk · J. R. Adams
+344 more
The transversity distribution, which describes transversely polarized quarksin transversely polarized nucleons, is a fundamental component of the spinstructure of the nucleon, and is only loosely constrained by global fits toexisting semi-inclusive deep inelastic scattering (SIDIS) data. In transverselypolarized $p^\uparrow+p$ collisions it can be accessed using transversepolarization dependent fragmentation functions which give rise to azimuthalcorrelations between the polarization of the struck parton and the final statescalar mesons. This letter reports on spin dependent di-hadron correlations measured by theSTAR experiment. The new dataset corresponds to 25 pb$^{-1}$ integratedluminosity of $p^\uparrow+p$ collisions at $\sqrt{s}=500$ GeV, an increase ofmore than a factor of ten compared to our previous measurement at$\sqrt{s}=200$ GeV. Non-zero asymmetries sensitive to transversity are observedat a $Q^2$ of several hundred GeV and are found to be consistent with theformer measurement and a model calculation. %we observe consistent with theformer measurement are observed.} We expect that these data will enable anextraction of transversity with comparable precision to current SIDIS datasetsbut at much higher momentum transfers where subleading effects are suppressed.
Journals
2018 EN
J. Adam · L. Adamczyk · J. R. Adams
+342 more
Flow harmonics ( v n ) in the Fourier expansion of the azimuthal distribution of particles are widely used to quantify the anisotropy in particle emission in high-energy heavy-ion collisions. The symmetric cumulants, S C ( m , n ) , are used to measure the correlations between different orders of flow harmonics. These correlations are used to constrain the initial conditions and the transport properties of the medium in theoretical models. In this Letter, we present the first measurements of the four-particle symmetric cumulants in Au+Au collisions at s N N = 39 and 200 GeV from data collected by the STAR experiment at RHIC. We observe that v 2 and v 3 are anti-correlated in all centrality intervals with similar correlation strengths from 39 GeV Au+Au to 2.76 TeV Pb+Pb (measured by the ALICE experiment). The v 2 – v 4 correlation seems to be stronger at 39 GeV than at higher collision energies. The initial-stage anti-correlations between second and third order eccentricities are sufficient to describe the measured correlations between v 2 and v 3 . The best description of v 2 – v 4 correlations at s N N = 200 GeV is obtained with inclusion of the system's nonlinear response to initial eccentricities accompanied by the viscous effect with η / s > 0.08 . Theoretical calculations using different initial conditions, equations of state and viscous coefficients need to be further explored to extract η / s of the medium created at RHIC.
Journals
2018 EN
STAR Collaboration · J. Adam · L. Adamczyk
+341 more
New measurements of directed flow for charged hadrons, characterized by theFourier coefficient \vone, are presented for transverse momenta $\mathrm{p_T}$,and centrality intervals in Au+Au collisions recorded by the STAR experimentfor the center-of-mass energy range $\mathrm{\sqrt{s_{_{NN}}}} = 7.7 - 200$GeV. The measurements underscore the importance of momentum conservation andthe characteristic dependencies on $\mathrm{\sqrt{s_{_{NN}}}}$, centrality and$\mathrm{p_T}$ are consistent with the expectations of geometric fluctuationsgenerated in the initial stages of the collision, acting in concert with ahydrodynamic-like expansion. The centrality and $\mathrm{p_T}$ dependencies of$\mathrm{v^{even}_{1}}$, as well as an observed similarity between itsexcitation function and that for $\mathrm{v_3}$, could serve as constraints forinitial-state models. The $\mathrm{v^{even}_{1}}$ excitation function couldalso provide an important supplement to the flow measurements employed forprecision extraction of the temperature dependence of the specific shearviscosity.
Journals
2018 EN
STAR Collaboration · L. Adamczyk · J. R. Adams
+343 more
Fluctuations of conserved quantities such as baryon number, charge, andstrangeness are sensitive to the correlation length of the hot and dense mattercreated in relativistic heavy-ion collisions and can be used to search for theQCD critical point. We report the first measurements of the moments of net-kaonmultiplicity distributions in Au+Au collisions at $\sqrt{s_{\rm NN}}$ = 7.7,11.5, 14.5, 19.6, 27, 39, 62.4, and 200 GeV. The collision centrality andenergy dependence of the mean ($M$), variance ($\sigma^2$), skewness ($S$), andkurtosis ($\kappa$) for net-kaon multiplicity distributions as well as theratio $\sigma^2/M$ and the products $S\sigma$ and $\kappa\sigma^2$ arepresented. Comparisons are made with Poisson and negative binomial baselinecalculations as well as with UrQMD, a transport model (UrQMD) that does notinclude effects from the QCD critical point. Within current uncertainties, thenet-kaon cumulant ratios appear to be monotonic as a function of collisionenergy.
Journals
2018 EN
J. Adam · L. Adamczyk · J. R. Adams
+336 more
We present a measurement of inclusive $J/\psi$ production at mid-rapidity ($|y|<1$) in $p+p$ collisions at a center-of-mass energy of $\sqrt{s}$ = 200 GeV with the STAR experiment at the Relativistic Heavy Ion Collider (RHIC). The differential production cross section for $J/\psi$ as a function of transverse momentum ($p_T$) for $0<p_T<14$ GeV/$c$ and the total cross section are reported and compared to calculations from the color evaporation model and the non-relativistic Quantum Chromodynamics model. The dependence of $J/\psi$ relative yields in three $p_T$ intervals on charged-particle multiplicity at mid-rapidity is measured for the first time in $p+p$ collisions at $\sqrt{s}$ = 200 GeV and compared with that measured at $\sqrt{s}$ = 7 TeV, PYTHIA8 and EPOS3 Monte Carlo generators, and the Percolation model prediction.