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Register a new userSpin alignment measurements using vector mesons with ALICE detector at the LHC
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Ranbir Singh
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We present new measurements related to spin alignment of $mathrm{K^{*0}}$ vector mesons at mid-rapidity for Pb-Pb collisions at $sqrt{s_{mathrm{NN}}}$ = 2.76 and 5.02 TeV. The spin alignment measurements are carried out with respect to production plane and second order event plane. At low $p_{mathrm{T}}$ the spin density matrix element $rho_{00}$ for $mathrm{K^{*0}}$ is found to have values slightly below 1/3, while it is consistent with 1/3, i.e. no spin alignment, at high $p_{mathrm{T}}$. Similar values of $rho_{00}$ are observed w.r.t. both production plane and event plane. Within statistical and systematic uncertainties, $rho_{00}$ values are also found to be independent of $sqrt{s_{mathrm{NN}}}$. $rho_{00}$ also shows centrality dependence with maximum deviation from 1/3 for mid-central collisions w.r.t. both the kinematic planes. The measurements for $mathrm{K^{*0}}$ in pp collisions at $sqrt{s}$ = 13 TeV and for $mathrm{K^{0}_{S}}$ (a spin 0 hadron) in 20-40% central Pb-Pb collisions at $sqrt{s_{mathrm{NN}}}$ = 2.76 TeV are consistent with no spin alignment.
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K. Schweda (Research Division
, ExtreMe Matter Institute EMMI
, GSIn Helmholtzzentrum fur Schwerionenforschung
2014
This is a brief summary of prompt production of D mesons in pp and Pb-Pb collisions with the ALICE apparatus at the LHC.
The Main Injector Particle Production (MIPP) experiment is a fixed target hadron production experiment at Fermilab. It measures particle production in interactions of 120 GeV/c primary protons from the Main Injector and secondary beams of $pi^{pm}, rm{K}^{pm}$, p and $bar{rm{p}}$ from 5 to 90 GeV/c on nuclear targets which include H, Be, C, Bi and U, and a dedicated run with the NuMI target. MIPP is a high acceptance spectrometer which provides excellent charged particle identification using Time Projection Chamber (TPC), Time of Flight (ToF), multicell Cherenkov (CKOV), Ring Imaging Cherenkov (RICH) detectors, and Calorimeter for neutrons. We present inelastic cross section measurements for 58 and 85 GeV/c p-H interactions, and 58 and 120 GeV/c p-C interactions. A new method is described to account for the low multiplicity inefficiencies in the interaction trigger using KNO scaling. Inelastic cross sections as a function of multiplicity are also presented. The MIPP data are compared with the Monte Carlo predictions and previous measurements. We also describe an algorithm to identify charged particles ($pi^{pm}/rm{p}/bar{rm{p}}$ etc.), and present the charged pion and kaon spectra from the interactions of 120 GeV/c protons with carbon target.
The ALICE experiment at the Large Hadron Collider (LHC) at CERN consists of a central barrel, a muon spectrometer and additional detectors for trigger and event classification purposes. The low transverse momentum threshold of the central barrel gives ALICE a unique opportunity to study the low mass sector of central exclusive production at the LHC.
We present the first spin alignment measurements for the $K^{*0}(892)$ and $phi(1020)$ vector mesons produced at mid-rapidity with transverse momenta up to 5 GeV/c at $sqrt{s_{NN}}$ = 200 GeV at RHIC. The diagonal spin density matrix elements with respect to the reaction plane in Au+Au collisions are $rho_{00}$ = 0.32 $pm$ 0.04 (stat) $pm$ 0.09 (syst) for the $K^{*0}$ ($0.8<p_T<5.0$ GeV/c) and $rho_{00}$ = 0.34 $pm$ 0.02 (stat) $pm$ 0.03 (syst) for the $phi$ ($0.4<p_T<5.0$ GeV/c), and are constant with transverse momentum and collision centrality. The data are consistent with the unpolarized expectation of 1/3 and thus no evidence is found for the transfer of the orbital angular momentum of the colliding system to the vector meson spins. Spin alignments for $K^{*0}$ and $phi$ in Au+Au collisions were also measured with respect to the particles production plane. The $phi$ result, $rho_{00}$ = 0.41 $pm$ 0.02 (stat) $pm$ 0.04 (syst), is consistent with that in p+p collisions, $rho_{00}$ = 0.39 $pm$ 0.03 (stat) $pm$ 0.06 (syst), also measured in this work. The measurements thus constrain the possible size of polarization phenomena in the production dynamics of vector mesons.
This article presents the basic idea of VHMPID, an upgrade detector for the ALICE experiment at LHC, CERN. The main goal of this detector is to extend the particle identification capabilities of ALICE to give more insight into the evolution of the hot and dense matter created in Pb-Pb collisions. Starting from the physics motivations and working principles the challenges and current status of development is detailed.
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