I. Chakaberia
A5000063101- Particle physics theoretical and experimental studies
- High-Energy Particle Collisions Research
- Quantum Chromodynamics and Particle Interactions
- Particle Detector Development and Performance
- Dark Matter and Cosmic Phenomena
- Cosmology and Gravitation Theories
- Nuclear reactor physics and engineering
- Neutrino Physics Research
- Black Holes and Theoretical Physics
- Astrophysics and Cosmic Phenomena
- Computational Physics and Python Applications
- Stochastic processes and statistical mechanics
- Distributed and Parallel Computing Systems
- Statistical Methods and Bayesian Inference
- Particle Accelerators and Free-Electron Lasers
- Theoretical and Computational Physics
- Scientific Computing and Data Management
- X-ray Spectroscopy and Fluorescence Analysis
- CCD and CMOS Imaging Sensors
- Superconducting Materials and Applications
- Atomic and Subatomic Physics Research
- Fusion materials and technologies
- Radiation Detection and Scintillator Technologies
- Nuclear physics research studies
- Crystallography and Radiation Phenomena
Lawrence Berkeley National Laboratory
2021-2025
European Organization for Nuclear Research
2012-2024
Lehigh University
2024
Indiana University Bloomington
2024
A. Alikhanyan National Laboratory
2022-2024
Czech Technical University in Prague
2024
Abilene Christian University
2019-2023
University of Houston
2018-2023
University of Jammu
2017-2023
Czech Academy of Sciences, Nuclear Physics Institute
2023
We present measurements of bulk properties the matter produced in Au+Au collisions at $\sqrt{s_{NN}}=$ 7.7, 11.5, 19.6, 27, and 39 GeV using identified hadrons ($\pi^\pm$, $K^\pm$, $p$ $\bar{p}$) from STAR experiment Beam Energy Scan (BES) Program Relativistic Heavy Ion Collider (RHIC). Midrapidity ($|y|<$0.1) results for multiplicity densities $dN/dy$, average transverse momenta $\langle p_T \rangle$ particle ratios are presented. The chemical kinetic freeze-out dynamics these energies...
Global polarization of $\Lambda$ hyperons has been measured to be the order a few tenths percent in Au+Au collisions at $\sqrt{s_{_{NN}}}$ = 200 GeV, with no significant difference between and $\bar{\Lambda}$. These new results reveal collision energy dependence global together previously observed 7.7 -- 62.4 GeV indicate noticeable vorticity medium created non-central heavy-ion highest RHIC energy. The signal is rough quantitative agreement theoretical predictions from hydrodynamic model...
The Λ (Λ[over ¯]) hyperon polarization along the beam direction has been measured in Au+Au collisions at sqrt[s_{NN}]=200 GeV, for first time heavy-ion collisions. dependence on hyperons' emission angle relative to elliptic flow plane exhibits a second harmonic sine modulation, indicating quadrupole pattern of vorticity component direction, expected due flow. is found increase more peripheral collisions, and shows no strong transverse momentum (p_{T}) p_{T} greater than 1 GeV/c. magnitude...
Non-monotonic variation with collision energy ($\sqrt{s_{\rm NN}}$) of the moments net-baryon number distribution in heavy-ion collisions, related to correlation length and susceptibilities system, is suggested as a signature for Quantum Chromodynamics (QCD) critical point. We report first evidence non-monotonic kurtosis times variance net-proton (proxy number) function \rootsnn 3.1$\sigma$ significance, head-on (central) gold-on-gold (Au+Au) collisions measured using STAR detector at RHIC....
The chiral magnetic effect (CME) is predicted to occur as a consequence of local violation $\mathcal{P}$ and $\mathcal{C}P$ symmetries the strong interaction amidst electromagnetic field generated in relativistic heavy-ion collisions. Experimental manifestation CME involves separation positively negatively charged hadrons along direction field. Previous measurements CME-sensitive charge-separation observables remain inconclusive because large background contributions. To better control...
The Breit-Wheeler process which produces matter and anti-matter from photon collisions is investigated experimentally through the observation of 6085 exclusive electron-positron pairs in ultra-peripheral Au+Au at $\sqrt{s_{_{NN}}}=200$ GeV. measurements reveal a large fourth-order angular modulation $\cos{4\Delta\phi}=(16.8\pm2.5)\%$ smooth invariant mass distribution absent vector mesons ($\phi$, $\omega$ $\rho$) experimental limit $\le 0.2\%$ observed yields. differential cross section as...
We report a systematic measurement of cumulants, $C_{n}$, for net-proton, proton and antiproton multiplicity distributions, correlation functions, $\kappa_n$, distributions up to the fourth order in Au+Au collisions at $\sqrt{s_{\mathrm {NN}}}$ = 7.7, 11.5, 14.5, 19.6, 27, 39, 54.4, 62.4 200 GeV. The $C_{n}$ $\kappa_n$ are presented as function collision energy, centrality kinematic acceptance rapidity, $y$, transverse momentum, $p_{T}$. data were taken during first phase Beam Energy Scan...
The deconfined quark-gluon plasma (QGP) created in relativistic heavy-ion collisions enables the exploration of fundamental properties matter under extreme conditions. Noncentral can produce strong magnetic fields on order <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:msup><a:mn>10</a:mn><a:mn>18</a:mn></a:msup><a:mtext> </a:mtext><a:mtext> </a:mtext><a:mi mathvariant="normal">G</a:mi></a:math>, which offers a probe into electrical conductivity QGP. In particular,...
The Proceedings of the 2011 workshop on Fundamental Physics at Intensity Frontier. Science opportunities intensity frontier are identified and described in areas heavy quarks, charged leptons, neutrinos, proton decay, new light weakly-coupled particles, nucleons, nuclei, atoms.
We report the first measurement of elliptic anisotropy (v_{2}) charm meson D^{0} at midrapidity (|y|<1) in Au+Au collisions sqrt[s_{NN}]=200 GeV. The was conducted by STAR experiment RHIC utilizing a new high-resolution silicon tracker. measured v_{2} 0%-80% centrality can be described viscous hydrodynamic calculation for transverse momentum (p_{T}) less than 4 GeV/c. as function kinetic energy (m_{T}-m_{0}, where m_{T}=sqrt[p_{T}^{2}+m_{0}^{2}]) is consistent with that light mesons 10%-40%...
Fluctuations of conserved quantities such as baryon number, charge, and strangeness are sensitive to the correlation length hot dense matter created in relativistic heavy-ion collisions can be used search for QCD critical point. We report first measurements moments net-kaon multiplicity distributions Au+Au at sNN=7.7, 11.5, 14.5, 19.6, 27, 39, 62.4, 200 GeV. The collision centrality energy dependence mean (M), variance (σ2), skewness (S), kurtosis (κ) well ratio σ2/M products Sσ κσ2...
We present measurements of π− and π+ elliptic flow, v2, at midrapidity in Au+Au collisions √sNN=200, 62.4, 39, 27, 19.6, 11.5, 7.7 GeV, as a function event-by-event charge asymmetry, Ach, based on data from the STAR experiment RHIC. find that (π+) flow linearly increases (decreases) with asymmetry for most centrality bins √sNN=27 GeV higher. At √sNN=200 slope difference v2 between Ach exhibits dependence, which is qualitatively similar to calculations incorporate chiral magnetic wave effect....
Collisions between prolate uranium nuclei are used to study how particle production and azimuthal anisotropies depend on initial geometry in heavy-ion collisions. We report the two- four-particle cumulants, $v_2\{2\}$ $v_2\{4\}$, for charged hadrons from U+U collisions at $\sqrt{s_{\rm NN}}$ = 193 GeV Au+Au 200 GeV. Nearly fully overlapping selected based amount of energy deposited by spectators STAR Zero Degree Calorimeters (ZDCs). Within this sample, observed dependence multiplicity...
We demonstrate a coincidence velocity map imaging apparatus equipped with novel time-stamping fast optical camera, Tpx3Cam, whose high sensitivity and nanosecond timing resolution allow for simultaneous position time-of-flight detection. This single detector design is simple, flexible, capable of highly differential measurements. show detailed characterization the camera its application in strong field ionization experiments.
The STAR Collaboration reports the measurement of semi-inclusive distributions charged-particle jets recoiling from a high transverse momentum hadron trigger, in central and peripheral $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{{s}_{\mathrm{NN}}}=200$ GeV. Charged are reconstructed with anti-${k}_{\mathrm{T}}$ algorithm for jet radii $R$ between 0.2 0.5 low infrared cutoff track constituents (${p}_{\mathrm{T}}>0.2 \mathrm{GeV}/\mathrm{c}$). A novel mixed-event technique is used to...
Dihadron angular correlations in d+Au collisions at sNN=200GeV are reported as a function of the measured zero-degree calorimeter neutral energy and forward charged hadron multiplicity Au-beam direction. A finite correlated yield is observed large relative pseudorapidity (Δη) on near side (i.e. azimuth Δϕ∼0). This Δη appears to scale with dominant, primarily jet-related, away-side (Δϕ∼π) yield. The Fourier coefficients Δϕ correlation, Vn=〈cosnΔϕ〉, have strong dependence. In addition, it...
We report first measurements of ${e}^{+}{e}^{\ensuremath{-}}$ pair production in the mass region $0.4<{M}_{ee}<2.6\text{ }\text{ }\mathrm{GeV}/{c}^{2}$ at low transverse momentum (${p}_{T}<0.15\text{ }\mathrm{GeV}/c$) noncentral $\mathrm{Au}+\mathrm{Au}$ collisions $\sqrt{{s}_{NN}}=200\text{ }\mathrm{GeV}$ and $\mathrm{U}+\mathrm{U}$ $\sqrt{{s}_{NN}}=193\text{ }\mathrm{GeV}$. Significant enhancement factors, expressed as ratios data over known hadronic contributions, are observed 40%--80%...
We present the measurement of transverse single-spin asymmetry weak boson production in transversely polarized proton-proton collisions at $\sqrt{s} = 500~\text{GeV}$ by STAR experiment RHIC. The measured observable is sensitive to Sivers function, one momentum dependent parton distribution functions, which predicted have opposite sign from that observed deep inelastic lepton-proton scattering. These data provide first experimental investigation non-universality fundamental our understanding QCD.
We report a new measurement of ${D}^{0}$-meson production at mid-rapidity $(|y|<1)$ in Au + collisions $\sqrt{{s}_{\mathrm{NN}}}=200\phantom{\rule{0.16em}{0ex}}\mathrm{GeV}$ utilizing the heavy flavor tracker, high resolution silicon detector STAR experiment. Invariant yields ${D}^{0}$ mesons with transverse momentum ${p}_{T}\ensuremath{\lesssim}9\phantom{\rule{0.16em}{0ex}}\mathrm{GeV}/c$ are reported various centrality bins (0--10%, 10--20%, 20--40%, 40--60%, and 60--80%). Blast-wave...
Global polarization of Ξ and Ω hyperons has been measured for the first time in Au+Au collisions at sqrt[s_{NN}]=200 GeV. The measurements Ξ^{-} Ξ[over ¯]^{+} hyperon have performed by two independent methods, via analysis angular distribution daughter particles parity violating weak decay Ξ→Λ+π, as well measuring Λ hyperon, polarized transfer from its parent. polarization, obtained combining results methods averaged over ¯]^{+}, is to be ⟨P_{Ξ}⟩=0.47±0.10(stat)±0.23(syst)% collision...
Rapidity-odd directed-flow measurements at midrapidity are presented for $\mathrm{\ensuremath{\Lambda}}$, $\overline{\mathrm{\ensuremath{\Lambda}}}$, ${K}^{\ifmmode\pm\else\textpm\fi{}}$, ${K}_{s}^{0}$, and $\ensuremath{\phi}$ $\sqrt{{s}_{NN}}=7.7$, 11.5, 14.5, 19.6, 27, 39, 62.4, 200 GeV in $\mathrm{Au}+\mathrm{Au}$ collisions recorded by the Solenoidal Tracker detector Relativistic Heavy Ion Collider. These greatly expand scope of data available to constrain models with differing...
We report the first measurement of rapidity-odd directed flow ($v_{1}$) for $D^{0}$ and $\overline{D^{0}}$ mesons at mid-rapidity ($|y| < 0.8$) in Au+Au collisions $\sqrt{s_{\rm NN}}$ = 200\,GeV using STAR detector Relativistic Heavy Ion Collider. In 10--80\% collisions, slope $v_{1}$ rapidity dependence ($dv_{1}/dy$), averaged over mesons, is -0.080 $\pm$ 0.017 (stat.) 0.016 (syst.) transverse momentum $p_{\rm T}$ above 1.5~GeV/$c$. The absolute value $D^0$-meson $dv_1/dy$ about 25 times...
Global hyperon polarization, $\overline{P}_\mathrm{H}$, in Au+Au collisions over a large range of collision energy, $\sqrt{s_\mathrm{NN}}$, was recently measured and successfully reproduced by hydrodynamic transport models with intense fluid vorticity the quark-gluon plasma. While na\"{i}ve extrapolation data trends suggests $\overline{P}_\mathrm{H}$ as energy is reduced, behavior at small $\sqrt{s_\mathrm{NN}}<7.7$ GeV unknown. Operating STAR experiment fixed-target mode, we polarization...
We report on the first measurement of charmed baryon Λ_{c}^{±} production at midrapidity (|y|<1) in Au+Au collisions sqrt[s_{NN}]=200 GeV collected by STAR experiment Relativistic Heavy Ion Collider. The Λ_{c}/D^{0} [denoting (Λ_{c}^{+}+Λ_{c}^{-})/(D^{0}+D[over ¯]^{0})] yield ratio is measured to be 1.08±0.16 (stat)±0.26 (sys) 0%-20% most central for transverse momentum (p_{T}) range 3<p_{T}<6 GeV/c. This significantly larger than pythia model calculations p+p collisions. ratio, as a...
We report on the measurements of directed flow $v_1$ and elliptic $v_2$ for hadrons ($\pi^{\pm}$, $K^{\pm}$, $K_{S}^0$, $p$, $\phi$, $\Lambda$ $\Xi^{-}$) from Au+Au collisions at $\sqrt{s_{NN}}$ = 3\,GeV $v_{2}$ $p$ $\overline{p}$) 27 54.4\,GeV with STAR experiment. While two higher energy midcentral number-of-constituent-quark (NCQ) scaling holds, midrapidity is negative all NCQ absent. In addition, slopes almost observed are found to be positive, implying dominant repulsive baryonic...