117012082
Search for narrow structures in the inclusive gamma ray spectrum resulting from proton-antiproton annihilation at rest
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.
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.
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.
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.
116328057
The KTeV Pure CsI Calorimeter
KTeV is currently building a state-of-the-art pure CsI electromagnetic calorimeter with a sophisticated digital readout. The CsI array is expected to have better than 1% resolution over a dynamic range of 2--64 GeV. The design of the CsI array is driven by the difficult physics goal of attempting to measure the CP violation parameter Re({epsilon}{prime}/{epsilon}) to 1 part in 10000 in a high-rate neutral beam environment. The physics requirements and their impact on the final design will be discussed.
119295507
Heavy lepton pair production in nucleus–nucleus collisions at LHC energy – a case study
Abstract We present a study of τ + τ − lepton pair production in Pb + Pb collisions at s NN = 5.5 TeV . The larger τ ± mass (∼1.77 GeV) compared to e ± and μ ± leads to considerably small hadronic contribution to the τ + τ − pair invariant mass ( M ) distribution relative to the production from thermal partonic sources. The quark–anti-quark annihilation processes via intermediary virtual photon, Z and Higgs bosons have been considered for the production of τ + τ − . We observe that the contribution from Drell–Yan process dominates over thermal yield for τ + τ − pair mass from 4 to 20 GeV at the LHC energy. We also present the ratio of τ lepton pair yields for nucleus–nucleus collisions relative to yields from p + p collisions scaled by number of binary collisions at LHC energies as a function τ pair mass. The ratio is found to be significantly above unity for the mass range 4 to 6 GeV. This indicates the possibility of detecting τ + τ − pair from quark–gluon plasma (QGP) in the mass window 4 ⩽ M (GeV) ⩽ 6 .
122237995
Chiral dynamics and operator relations at non-zero chemical potential
We discuss Taylor expansions of operator expectation values in QCD with respect to chemical potentials of quarks. Maxwell's relations between coefficients and Ward identities between series are used to relate the operators which give the Taylor coefficients of the series for the chiral condensate, the pseudoscalar susceptibility and the mass dependence of quark number susceptibilities. Through such relations the physics of chiral dynamics are explored. The renormalized expectation values of the chiral condensate and its Taylor coefficients are extracted from simulation.
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.
17726542
Formation and collapse of false vacuum bubbles in relativistic heavy-ion collisions
Abstract It is possible that under certain situations, in a relativistic heavy-ion collision, partons may expand out forming a shell like structure. We analyze the process of hadronization in such a picture for the case when the quark–hadron transition is of first order, and argue that the inside region of such a shell must correspond to a supercooled (to T=0 ) deconfined vacuum. Hadrons from that region escape out, leaving a bubble of pure deconfined vacuum with large vacuum energy. This bubble undergoes relativistic collapse, with highly Lorentz contracted bubble walls, and may concentrate the entire energy into extremely small regions. Eventually different portions of bubble wall collide, with the energy being released in the form of particle production. Thermalization of this system can lead to very high temperatures. With a reasonably conservative set of parameters, at LHC, the temperature of the hot spot can reach as high as 3 GeV, and well above it with more optimistic parameters. Such a hot spot can leave signals like large P T partons, dileptons, and enhanced production of heavy quarks. We also briefly discuss a speculative possibility where the electroweak symmetry may get restored in the highly dense region resulting from the decay of the bubble wall via the phenomenon of non-thermal symmetry restoration (which is usually employed in models of pre-heating after inflation). If that could happen then the possibility may arise of observing sphaleron induced baryon number violation in relativistic heavy-ion collisions.
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.