122001456
A trigger for the Fermilab E760 lead-glass calorimeter
Abstract The E760 #1 experiment at Fermi National Laboratory has been commissioned to study electromagnetic decay channels of charmonium states. A trigger has been built for the 1280-element lead-glass calorimeter to facilitate the study of all-neutral decay modes. The trigger has also proven to be extremely useful for charged electromagnetic final states. The trigger has been successfully deployed and has shown itself to be reliable and highly efficient. The design and performance of this trigger are described in detail.
126084521
Measurements of the widths of charmonium states at the Fermilab anti-p accumulator ring
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.
125360362
A program to measure the direct CP violating decay K(L) --> pi0 nu anti-nu and other rare decays at Fermilab using the main injector
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.
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.
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 .
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.
41160767
Chiral dynamics in QCD at finite chemical potential
We present the renormalized Taylor expansion of the chiral condensate with chemical potential. The relation with the Taylor coefficients of meson susceptibilities and the quark mass dependence of the quark number susceptibilities are obtained through chiral Ward identities and Maxwell relations. The continuum limit is obtained in quenched and two flavor QCD. In N{sub f}=2 QCD, the quadratic response coefficients of the chiral condensate to chemical potential indicate that pion fluctuations decrease at finite chemical potential toward the critical end point. We discuss how these observables can be used to test other features of the QCD phase diagram.
15200778
Measuring cosmic defect correlations in liquid crystals
From the theory of topological defect formation proposed for the early universe, the so called Kibble mechanism, it follows that the density correlation functions of defects and anti-defects in a given system should be completely determined in terms of a single length scale $\xi$, the relevant domain size. Thus, when lengths are expressed in units of $\xi$, these distributions should show universal behavior, depending only on the symmetry of the order parameter, and space dimensions. We have verified this prediction by analyzing the distributions of defects/anti-defects formed in the isotropic-nematic phase transition in a thin layer of nematic liquid crystals. Our experimental results confirm this prediction and are in reasonable agreement with the results of numerical simulations.
11476051
Observing Correlated Production of Defects and Antidefects in Liquid Crystals
We present observations of strength one defects and antidefects formed in isotropic-nematic phase transition in a thin layer of nematic liquid crystals, using a cross-polarizer setup. We measure the widths of the distributions of {\it net} winding number in small regions, and determine the exponent characterizing the correlation between defects and antidefects to be 0.26$\pm$0.11, in very good agreement with the value 1/4 predicted by the Kibble mechanism for defect production. We also describe a novel technique to determine the director distribution in observations of defect networks.