123205836
The E760 lead-glass central calorimeter: design and initial test results
The central calorimeter in Fermilab experiment E760++ has been designed to measure the topology and energies of electrons and photons in the decay of charmonium formed in pp annihilation. The calorimeter is composed of 1280 lead-glass Cherenkov counters read out with photomultiplier tubes. This paper discusses design criteria for the calorimeter and describes how these criteria were met. Data from tests in low energy (10–84 MeV) and medium energy (1–4 GeV) beams are presented showing a spatial resolution of 9 mm, an energy resolution of (3.0 ± 0.3)%√E[GeV] + (1.5 ± 0.5)%, and an effective energy threshold below 10 MeV.
116924174
Search for new strange resonances in inclusive charged kaon spectra from p̄p annihilation at rest
Charged spectra from pp annihilations at rest have been measured using the PS183 spectrometer at LEAR. From these data, charged kaon spectra are produced using time‐of‐flight separation. The spectra show structures corresponding to annihilation into the K±K−+ and K*±K−+ channels. A search for structures indicating other resonances is discussed.
38259728
Search for narrow states in the inclusive gamma -ray spectra resulting from antiproton annihilations at rest in liquid hydrogen and deuterium.
The energy spectrum of {gamma} rays produced in proton-antiproton annihilation at rest in hydrogen and deuterium has been measured with good energy resolution and high statistics. The data were taken using the PS183 magnetic pair spectrometer at CERN's Low Energy Antiproton Ring. A detailed search of the {gamma} spectrum yielded no evidence of {gamma} transitions to narrow states with widths consistent with the spectrometer resolution. In hydrogen, upper limits (95% C.L.) are obtained for the yield of narrow states of (2--5){times}10{sup {minus}4} for states below 1700 MeV/{ital c}{sup 2}, and (5--10){times}10{sup {minus}4} for states between 1700 and 1800 MeV/{ital c}{sup 2}. In deuterium, the corresponding upper limits are (1--7){times}10{sup {minus}3} for masses between 700 and 1730 MeV/{ital c}{sup 2}, and (1--2){times}10{sup {minus}3} for masses between 1750 and 1835 MeV/{ital c}{sup 2}. These results contradict reports of the observation of narrow lines made by previous experiments.
118019702
Search for resonance structures in inclusive charged pion spectra from p̄p annihilation at rest
The charged pion momentum spectra from pp annihilation at rest have been measured with high statistics. A search for structures finds four narrow lines which are identified with the absorption and decay processes of kaons stopping in the target. Limits of 1‐6×10−4/p (90% C.L.) are placed on the yield of a narrow state in the mass range 1000–1660 MeV.
123588442
A search for structure in charged meson spectra from proton-antiproton annihilations at rest
The charged meson momentum spectra from pp annihilation at rest have been measured with high statistics. A search is made for structures between 150 and 300 MeV/c which indicate narrow baryonium states. We find four narrow lines which are identified with the absorption and decay processes of kaons stopping in the target. No other narrow structures are seen, giving limits of 2−6×10−4 p (90% CL) for the yield of a narrow state in the mass range 1510–1660 MeV.
39950378
Measurement of the gamma gamma partial width of the chi 2 charmonium resonance.
The E760 Collaboration has studied the reaction [ital [bar p]p][r arrow][chi][sub 2][r arrow][gamma][gamma] using a hydrogen gas jet target in the Fermilab antiproton acumulator ring. The following values are obtained for the branching ratio and partial width to two photons; [ital B]([chi][sub 2][r arrow][gamma][gamma])=(1.60[plus minus]0.45)[times]10[sup [minus]4] and [Gamma]([chi][sub 2][r arrow][gamma][gamma])=321[plus minus]95 eV.
119102585
Thermodynamic properties of strongly interacting matter in a finite volume using the Polyakov–Nambu–Jona-Lasinio model
We present the thermodynamic properties of strongly interacting matter in finite volume in the framework of Polyakov loop enhanced Nambu$-$Jona-lasinio model within mean field approximation. We considered both the 2 flavor and 2+1 flavor matter. Our primary observation was a qualitative change in the phase transition properties that resulted in the lowering of the temperature corresponding to the critical end point. This would make it favorable for detection in heavy-ion experiments that intend to create high density matter with considerably small temperatures. We further demonstrate the possibility of obtaining chiral symmetry restoration even within the confined phase in finite volumes.
18912380
Sustaining supercooled mixed phase via resonant oscillations of the order parameter
We investigate the dynamics of a first order transition when the order parameter field undergoes resonant oscillations, driven by a periodically varying parameter of the free energy. This parameter could be a background oscillating field as in models of pre-heating after inflation. In the context of condensed matter systems, it could be temperature T, or pressure, external electric/magnetic field etc. We show that with suitable driving frequency and amplitude, the system remains in a type of mixed phase, without ever completing transition to the stable phase, even when the oscillating parameter of the free energy remains below the corresponding critical value (for example, with oscillating temperature, T always remains below the critical temperature Tc). This phenomenon may have important implications. In cosmology, it will imply prolonged mixed phase in a first order transition due to coupling with background oscillating fields. In condensed matter systems, it will imply that using oscillating temperature (or, more appropriately, pressure waves) one may be able to sustain liquids in a mixed phase indefinitely at low temperatures, without making transition to the frozen phase.
119158093
The consequences of SU (3) colorsingletness, Polyakov Loop and Z (3) symmetry on a quark–gluon gas
Based on quantum statistical mechanics we show that the SU(3) color singlet ensemble of a quark-gluon gas exhibits a Z(3) symmetry through the normaized character in fundamental representation and also becomes equivalent, within a stationary point approximation, to the ensemble given by Polyakov Loop. Also Polyakov Loop gauge potential is obtained by considering spatial gluons along with the invariant Haar measure at each space point. The probability of the normalized character in SU(3) vis-a-vis Polyakov Loop is found to be maximum at a particular value exhibiting a strong color correlation. This clearly indicates a transition from a color correlated to uncorrelated phase or vise-versa. When quarks are included to the gauge fields, a metastable state appears in the temperature range 145 T(MeV) 170 due to the explicit Z(3) symmetry breaking in the quark-gluon system. Beyond T 170 MeV the metastable state disappears and stable domains appear. At low temperature a dynamical recombination of ionized Z(3) color charges to a color singlet Z(3) confined phase is evident along with a confining background that originates due to circulation of two virtual spatial gluons but with conjugate Z(3) phases in a closed loop. We also discuss other possible consequences of the center domains in the color deconfined phase at high temperature.
119209903
Study of Beta Equilibrated 2+1 Flavor Quark Matter in PNJL Model
We present a first case study of the phase diagram of 2+1 flavor strongly interacting matter in β−equilibrium, using the Polyakov−Nambu−Jona-Lasinio model. This condition is relevant for the study of physics of neutron star. Physical characteristics of a number of thermodynamic observables have been presented, and their variation with the changing environmental conditions discussed. Comparative analysis with the corresponding situation in the Nambu-Jona-Lasinio model is presented.
121968392
Observing B-violation in relativistic heavy-ion collisions
Under certain situations, partons formed in heavy-ion collision experiments may expand out forming a shell-like structure. The partons in the outer shell subsequently hadronize, leaving a bubble of pure deconfined vacuum for a first-order quark-hadron phase transition. The bubble collapses and may eventually decay into particles which may thermalize to temperatures exceeding the electroweak transition temperature (100 GeV) at LHC. This will lead to the possibility of unsuppressed electroweak baryon number violating processes.