Energy Correlators within Jets in Transversely Polarized Proton-Proton Collisions at โs =200 GeV
Explore the source record for details and available documents.
73 NUCLEAR PHYSICS AND RADIATION PHYSICSโ
Engineering topics
Cai, X. Z.
Publications and source records attributed to Cai, X. Z..
Tracking the baryon number with nuclear collisions
Explore the source record for details and available documents.
73 NUCLEAR PHYSICS AND RADIATION PHYSICSโ
First Observation of Deuteron-ฮ Correlations at RHIC
Explore the source record for details and available documents.
73 NUCLEAR PHYSICS AND RADIATION PHYSICSโ
Measuring spin correlation between quarks during QCD confinement
The vacuum is now understood to have a rich and complex structure, characterized by fluctuating energy fields and a condensate of virtual quarkโantiquark pairs. The spontaneous breaking of the approximate chiral symmetry, signalled by the nonvanishing quark condensate $\langle$$q\bar{q}$$\rangle$, is dynamically generated through topologically nontrivial gauge configurations such as instantons. The precise mechanism linking the chiral symmetry breaking to the mass generation associated with quark confinement remains a profound open question in quantum chromodynamics (QCD)โthe fundamental theory of strong interaction. High-energy protonโproton collisions could liberate virtual quarkโantiquark pairs from the vacuum that subsequently undergo confinement to form hadrons, whose properties could serve as probes into QCD confinement and the quark condensate. Here we report evidence of spin correlations in $ฮ\bar{ฮ}$ hyperon pairs inherited from spin-correlated strange quarkโantiquark virtual pairs. Measurements by the STAR experiment at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory reveal a relative polarization signal of (18 ยฑ 4)% that links the virtual spin-correlated quark pairs from the QCD vacuum to their final-state hadron counterparts. Crucially, this correlation vanishes when the hyperon pairs are widely separated in angle, consistent with the decoherence of the quantum system. Our findings provide a new experimental model for exploring the dynamics and interplay of quark confinement and entanglement.
73 NUCLEAR PHYSICS AND RADIATION PHYSICSโ
Temperature measurement of Quark-Gluon plasma at different stages
In a Quark-Gluon Plasma (QGP), the fundamental building blocks of matter, quarks and gluons, are under extreme conditions of temperature and density. A QGP could exist in the early stages of the Universe, and in various objects and events in the cosmos. The thermodynamic and hydrodynamic properties of the QGP are described by Quantum Chromodynamics (QCD) and can be studied in heavy-ion collisions. Despite being a key thermodynamic parameter, the QGP temperature is still poorly known. Thermal lepton pairs (e + e โ and ฮผ + ฮผ โ ) are ideal penetrating probes of the true temperature of the emitting source, since their invariant-mass spectra suffer neither from strong final-state interactions nor from blue-shift effects due to rapid expansion. Here we measure the QGP temperature using thermal e+eโ production at the Relativistic Heavy Ion Collider (RHIC). The average temperature from the low-mass region (in-medium ฯ 0 vector-meson dominant) is (2.01 ยฑ 0.23) ร 10 12 K, consistent with the chemical freeze-out temperature from statistical models and the phase transition temperature from Lattice QCD. The average temperature from the intermediate mass region (above the ฯ0 mass, QGP dominant) is significantly higher at (3.25 ยฑ 0.60) ร 10 12 K. This work provides essential experimental thermodynamic measurements to map out the QCD phase diagram and understand the properties of matter under extreme conditions.
73 NUCLEAR PHYSICS AND RADIATION PHYSICSโ
Semi-inclusive direct photon + jet and ๐ 0 + jet correlations measured in ๐ + ๐ and central Au + Au collisions at $\sqrt{s_{NN}}$ = 200GeV
The STAR experiment at RHIC reports new measurements of jet quenching based on the semi- inclusive distribution of charged-particle jets recoiling from direct photon (ฮณ dir ) and neutral pion (ฯ 0 ) triggers in pp and central Au + Au collisions at $\sqrt{s_{NN}}$ = 200 GeV, for triggers in the range 9 < $E$$^{trig}_{T}$ < 20 GeV. The datasets have integrated luminosities of 3.9nb โ1 for Au + Au and 23pb โ1 for ๐๐ collisions. Jets are reconstructed using the anti-๐ ๐ algorithm with resolution parameters ๐ = 0.2 and 0.5. The large uncorrelated jet background in central Au + Au collisions is corrected using a mixed-event approach, which enables precise charged-particle jet measurements at low transverse momentum ๐$^{ch}_{๐,jet}$ and large ๐ . Recoil-jet distributions are reported in the range ๐$^{ch}_{๐,jet}$ < 25 GeV/๐. Comparison of the distributions measured in ๐๐ and Au + Au collisions reveals strong medium-induced jet yield suppression for ๐ = 0.2 with markedly less suppression for ๐ = 0.5. Comparison is also made to theoretical models incorporating jet quenching. Furthermore, these data provide new insight into the mechanisms underlying jet quenching and the angular dependence of medium-induced jet-energy transport and provide new constraints on modeling such effects.
73 NUCLEAR PHYSICS AND RADIATION PHYSICSโ