arXiv subjects

Zebo Tang

Publications and source records attributed to Zebo Tang.

At least 55 records · Page 3Linked to original sources

arXiv2019

Extensive beam test study of prototype MRPCs for the T0 detector at the CSR external-target experiment

The CSR External-target Experiment (CEE) will be the first large-scale nuclear physics experiment device at the Cooling Storage Ring (CSR) of the Heavy-Ion Research Facility in Lanzhou (HIRFL) in China. A new T0 detector has been proposed to measure the multiplicity, angular distribution and timing information of charged particles produced in heavy-ion collisions at the target region. Multi-gap resistive plate chamber (MRPC) technology was chosen as part of the construction of the T0 detector, which provides precision event collision times (T0) and collision geometry information. The prototype was tested with hadron and heavy-ion beams to study its performance. By comparing the experimental results with a Monte Carlo simulation, the time resolution of the MRPCs are found to be $\sim$ 50 ps or better. The timing performance of the T0 detector, including both detector and readout electronics, we found to fulfil the requirements of the CEE.

physics.ins-det↗

arXiv2019

Initial transverse-momentum broadening of Breit-Wheeler process in relativistic heavy-ion collisions

We calculate the cross section and transverse-momentum ($P_{\bot}$) distribution of the Breit-Wheeler process in relativistic heavy-ion collisions and their dependence on collision impact parameter ($b$). To accomplish this, the Equivalent Photon Approximation (EPA) was generalized in a more differential way compared to the approach traditionally used for inclusive collisions. In addition, a lowest-order QED calculation with straightline assumption was performed as a standard baseline for comparison. The cross section as a function of $b$ is consistent with previous calculations using the equivalent one-photon distribution function. Most importantly, the $P_{\bot}$ shape from this model is strongly dependent on impact parameter and can quantitatively explain the $P_{\bot}$ broadening observed recently by RHIC and LHC experiments. This broadening effect from the initial QED field strength should be considered in studying possible trapped magnetic field and multiple scattering in a Quark-Gluon Plasma (QGP). The impact-parameter sensitive observable also provides a controllable tool for studying extreme electromagnetic fields.

nucl-th↗

arXiv2018

Photoproduction of J/$ψ$ in non-single-diffractive p+p collisions

Recently, significant enhancements of J/$ψ$ production at very low transverse momenta were observed by the ALICE and STAR collaboration in peripheral hadronic A+A collisions. The anomaly excesses point to evidence of coherent photon-nucleus interactions in violent hadronic heavy-ion collisions, which were conventionally studied only in ultra-peripheral collisions. Assuming that the coherent photoproduction is the underlying mechanism which is responsible for the excess observed in peripheral A+A collisions, its contribution in p+p collisions with nuclear overlap, i.e. non-single-diffractive collisions, is of particular interest. In this paper, we perform a calculation of exclusive J/$ψ$ photoproduction in non-single-diffractive p+p collisions at RHIC and LHC energies base on the pQCD motivated parametrization from world-wide experimental data, which could be further employed to improve the precision of phenomenal calculations for photoproduction in A+A collisions. The differential rapidity and transverse momentum distributions of J/$ψ$ from photoproduction are presented. In comparison with the J/$ψ$ production from hadronic interactions, we find that the contribution of photoproduction is negligible.

hep-ph↗

arXiv2018

Double-slit experiment at fermi scale: coherent photoproduction in heavy-ion collisions

The double-slit experiment has become a classic thought experiment, for its clarity in expressing the central puzzle of quantum mechanics -- wave-particle complementarity. Such wave-particle duality continues to be challenged and investigated in a broad range of entities with electrons, neutrons, helium atoms, C$_{60}$ fullerenes, Bose-Einstein condensates and biological molecules. All existing experiments are performed with the scale larger than angstrom. In this article, we present a double-slit scenario at fermi scale with new entities -- coherent photon products in heavy-ion collisions. Virtual photons from the electromagnetic fields of relativistic heavy ions can fluctuate to quark-antiquark pairs, scatter off a target nucleus and emerge as vector mesons. The two colliding nuclei can take turns to act as targets, forming a double-slit interference pattern. Furthermore, the `which-way' information can be partially solved by the violent strong interactions in the proposed scenario, which demonstrates a key concept of quantum mechanics -- complementary principle.

hep-ph↗

arXiv2018

Coherent photo-produced J$/ψ$ and dielectron yields in isobaric collisions

Recently, significant enhancements of J/$ψ$ and $e^{+} e^{-}$ pair production at very low transverse momenta were observed by the STAR and ALICE collaboration in peripheral hadronic A+A collisions. The anomaly excesses point to evidence of coherent photon-nucleus and photon-photon interactions in violent hadronic heavy-ion collisions, which were conventionally studied only in ultra-peripheral collisions. The isobaric collisions performed at RHIC provides a unique opportunity to test the existence of coherent photon products in hadronic heavy-ion collisions. The idea is that the possible production of coherent photon products is significantly different in different collision systems due to the variations in their charge and nuclear density distributions. In this letter, we focus on the peripheral collisions and provide theoretical predictions for coherent production of J/$ψ$ and dielectron in isobaric collisions. We show that the expected yields differ significantly to perform the experimental test.

hep-ph↗

arXiv2018

Probing vorticity structure in heavy-ion collisions by local $Λ$ polarization

We study the local structure of the vorticity field and the $Λ$ polarization in Au+Au collisions in the energy range $\sqrt{s_{\mathrm{NN}}}=7.7$--$200$ GeV and Pb+Pb collisions at $\sqrt{s_{\mathrm{NN}}}=2760$ GeV using A Multi-Phase Transport (AMPT) model. We focus on the vorticity field arising from the non-uniform expansion of the fireball, which gives the circular structure of the transverse vorticity $\boldsymbolω_{\perp}=(ω_{x},ω_{y})$ around the $z$ direction as well as the quadrupole pattern of the longitudinal vorticity $ω_{z}$ in the transverse plane. As a consequence, the three components of the polarization vector $\mathbf{P}=(P_{x},P_{y},P_{z})$ for $Λ$ hyperons show harmonic behaviors as $\mathrm{sgn}(Y)\sinϕ_{p}$, $-\mathrm{sgn}(Y)\cosϕ_{p}$, and $-\sin(2ϕ_{p})$, where $ϕ_{p}$ and $Y$ are the azimuthal angle and rapidity in momentum space. These patterns of the local $Λ$ polarization are expected to be tested in future experiments.

nucl-th↗

arXiv2018

Multiplicity Dependence of Charged Particle, $ϕ$ Meson and Multi-strange Particle Productions in p+p Collisions at $\sqrt{\rm s}$ = 200 GeV with PYTHIA Simulation

We report the multiplicity dependence of charged particle productions for $π^{\pm}$, $K^{\pm}$, $p$, $\overline{p}$ and $ϕ$ meson at $|y| < 1.0$ in p+p collisions at $\sqrt{\rm s}$ = 200 GeV with $\rm PYTHIA$ simulation. The impact of parton multiple interactions and gluon contributions is studied and found to be possible sources of the particle yields splitting as a function of $p_T$ with respect to multiplicity. No obvious particle species dependence for the splitting is observed. The multiplicity dependence on ratios of $K^-/π^-$, $K^+/π^+$, $\overline{p}/π^-$, $p/π^+$ and $Λ/K^{0}_{s}$ in mid-rapidity in p+p collisions is found following the similar tendency as that in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV from RHIC, which heralds the similar underlying initial production mechanisms despite the differences in the initial colliding systems.

hep-ph↗

arXiv2015

Systematic study of the experimental measurements on $J/ψ$ cross section and kinematic distribution in $p+p$ collisions at different energies

The world experimental data on cross section and kinematic distribution in $p+p$ and $p+A$ collisions at $\sqrt{s}$ = 6.8 - 7000 GeV are examined in systematic way. The $\sqrt{s}$ dependence of the inclusive cross section, rapidity and transverse momentum distributions are studied phenomenologically. We explore empirical formulas to obtain the total cross section, rapidity and transverse momentum ($p_{T}$) distribution. This is crucial for the interpretation of A$+$A $J/ψ$ results at RHIC when the $p+p$ reference data are not available. In addition, the cross section at mid-rapidity and transverse momentum distributions in $p+p$ collisions at $\sqrt{s}$ = 39 and 62.4 GeV are evaluated.

hep-ex↗

arXiv2015

A Cosmic Ray Test Platform Based on the High Time Resolution MRPC Technology

In order to test the performance of detector/prototype in environment of laboratory, we design and build a larger area ($90\times52$ $cm^2$) test platform of cosmic ray based on well-designed Multi-gap Resistive Plate Chamber (MRPC) with an excellent time resolution and a high detection efficiency for the minimum ionizing particles (MIPs). The time resolution of the MRPC module used is tested to be ~80 ps, and the position resolution along the strip is ~5 mm, while the position resolution perpendicular to the strip is ~12.7 mm. The platform constructed by four MRPC modules can be functional for tracking the cosmic rays with a spatial resolution ~6.3 mm, and provide a reference time ~40 ps.

physics.ins-det↗

arXiv2014

Onset of radial flow in p+p collisions

It has been debated for decades whether hadrons emerging from p+p collisions exhibit collective expansion. The signal of the collective motion in p+p collisions is not as clear/clean as in heavy-ion collisions because of the low multiplicity and large fluctuation in p+p collisions. Tsallis Blast-Wave (TBW) model is a thermodynamic approach, introduced to handle the overwhelming correlation and fluctuation in the hadronic processes. We have systematically studied the identified particle spectra in p+p collisions from RHIC to LHC using TBW and found no appreciable radial flow in p+p collisions below $\sqrt{s}=900$ GeV. At LHC higher energy of 7 TeV in p+p collisions, the radial flow velocity achieves an average value of $<β>= 0.320\pm0.005$. This flow velocity is comparable to that in peripheral (40-60%) Au+Au collisions at RHIC. Breaking of the identified particle spectra $m_T$ scaling was also observed at LHC from a model independent test.

nucl-ex↗

arXiv2014

Charmonium Transverse Momentum Distribution in High Energy Nuclear Collisions

The Charmonium transverse momentum distribution is more sensitive to the nature of the hot QCD matter created in high energy nuclear collisions, in comparison with the yield. Taking a detailed transport approach for charmonium motion together with a hydrodynamic description for the medium evolution, the cancelation between the two hot nuclear matter effects, the dissociation and the regeneration, controls the charmonium transverse momentum distribution. Especially, the second moment of the distribution can be used to differentiate between the hot mediums produced at SPS, RHIC and LHC energies.

nucl-th↗

arXiv2014

A Large area GEM Detector Using an improved Self-stretch Technique

A GEM detector with an effective area of 30*30 cm2 has been constructed using an improved self-stretch technique, which enables an easy and fast GEM assembling. The design and assembling of the detector is described. Results from tests of the detector with 8 keV X-rays on effective gain and energy resolution are presented.

physics.ins-det↗

arXiv2013

Systematic study of the experimental measurements on ratios of different $Υ$ states

The world data on yields and ratios of different $Υ$ states created in hadron collisions at $\sqrt{s} = 19-8000$ GeV are examined in systematic way. We find that $Υ(2S)/Υ(1S)=0.275\pm0.005$ and $Υ(3S)/Υ(1S)=0.128\pm0.004$. No signficant energy dependence of these ratios are observed within the broad collision energies. In addition, the rapidity, transverse momentum, and transverse mass dependence of these ratios are also reported.

hep-ex↗

arXiv2011

Hadronic Trigger using electromagnetic calorimeter and particle identification at high-pT with STAR Detector

We derive a new method to improve the statistics of identified particles at high transverse momentum (\pt) using online-triggered events by the Barrel Electro-Magnetic-Calorimeter (BEMC) detector. The BEMC is used to select hadronic interaction and energy deposit from showers created by charged hadrons ($π^{\pm},K^{\pm}$ and $p$($\bar{p}$)) in the BEMC. With this trigger, the statistics of the high \pt particles are significantly enhanced by about a factor of 100 with selection efficiency up to 20%. In addition, resonant states ($ρ^0$, $K^{\star}$) and weak-decay V0 (\Ks and \La(\aLa)) can be constructed by selecting the BEMC-trigger hadron as one of its daughters. We also show that the trigger efficiency can be obtained reliably in simulation and data-driven approaches.

hep-ex↗

arXiv2011

Statistical Origin of Constituent-Quark Scaling in the QGP hadronization

Nonextensive statistics in a Blast-Wave model (TBW) is implemented to describe the identified hadron production in relativistic p+p and nucleus-nucleus collisions. Incorporating the core and corona components within the TBW formalism allows us to describe simultaneously some of the major observations in hadronic observables at the Relativistic Heavy-Ion Collider (RHIC): the Number of Constituent Quark Scaling (NCQ), the large radial and elliptic flow, the effect of gluon saturation and the suppression of hadron production at high transverse momentum (pT) due to jet quenching. In this formalism, the NCQ scaling at RHIC appears as a consequence of non-equilibrium process. Our study also provides concise reference distributions with a least chi2 fit of the available experimental data for future experiments and models.

nucl-ex↗

arXiv2011

J/psi production and correlation in p+p and Au+Au collisions at STAR

The results on J/psi pT spectra in 200 GeV p+p and Au+Au collisions at STAR with pT in the range of 3-10 GeV/c are presented. Nuclear modification factor of high-pT J/psi is found to be consistent with no suppression in peripheral Au+Au collisions and significantly smaller than unity in central Au+Au collisions. The J/psi elliptic flow is measured to be consistent with no flow at pT < 10 GeV/c in 20-60% Au+Au collisions.

hep-ex↗

arXiv2010

Beam test of signal cross-talk and transmission for LMPRC

A new prototype of large area Multi-gap Resistive Plate Chamber (MRPC) with long readout strips was built. This Long-strip Multi-gap Resistive Plate Chamber (LMRPC) is double stacked and has ten 250 $μ$m-thick gas gaps. Signals are read out from two ends of strip with an active area of 50 cm$\times$2.5 cm in each. The detector was tested at FOPI in GSI, using the secondary particles of proton beams ($E = 3.5 GeV$) colliding with a Pb target. The results show that the LMRPC prototype has a time resolution of about 60$\sim$70 ps; the detecting efficiency is over 98% and the ratio of cross-talk is lower than 2%. The detector also has a good spatial resolution of 0.36 cm along the strip direction.

physics.ins-det↗

arXiv2010

J/psi production at high pT at STAR

We report results on J/psi-hadron azimuthal angular correlations in 200 GeV p+p collision in the STAR experiment at RHIC. The extracted B-hadron feed-down contribution to inclusive J/psi yield is found to be 10-25% in 4<p_T<12 GeV/c and has no significant center-of-mass energy dependence from RHIC to LHC. The p_T spectrum of charged hadron associated with high-p_T J/psi triggers on the away side is found to be consistent with that from di-hadron correlations. J/psi signal from partially produced Au+Au 39 GeV data will also be presented to demonstrate STAR's J/psi capability at RHIC low energy run.

hep-ex↗