122648978
Strangeness and hadronization from a quark-gluon plasma☆
Abstract From a phenomenological equation of state, the role of strangeness in the hadronizing QGP is studied. Even though strangeness abundance of the QGP is similar to that of an equilibrium hadron gas, the characteristic change in the slope of energy spectra of K + and K − mesons can serve as a signature of QGP.
124365920
A statistical model analysis of the rapidity distribution of hadrons
121511469
The ϱ-peak in the dimuon spectrum as a clock for fireball lifetimes in relativistic nuclear collisions
Abstract We discuss the modification of the dipleton yield from vector mesons inside a nuclear fireball. We argue that the relative magnitude of the ϱ peak in the dilepton spectrum determines the lifetime of the hadron gas phase in nuclear collisions with an accuracy of about 1 fm/ c . We also find that the φ (ω + ϱ) ratio measured in the dimuon channel in 200 A GeV O + U and S + U collisions points towards a rather short-lived hadronic phase in these collisions.
118425306
Two freeze-out model for the hadrons produced in the Relativistic Heavy-Ion Collisions
An expanding fireball model with two freeze-outs, which assumes that the chemical freeze-out occurs earlier at higher temperature and the thermal freeze-out occurs later at lower temperature, is developed and successfully applied to fit simultaneously the hadron ratios, transverse momentum spectra of measured hadrons and rapidity distribution of charged hadrons measured in Au+Au collision at 200 A·GeV by STAR, PHENIX and PHOBOS collaborations. The quality of all the fittings is very good and the resulting parameters are in agreement with published values.
119332767
Analysis of Low-Energy Pion Spectra
The transverse mass spectra and the rapidity distributions of $\pi^+$ and $\pi^-$ in Au-Au collisions at 2, 4, 6, and 8 GeV$\cdot$A by E895 collaboration are fitted using an elliptically expanding fireball model with the contribution from the resonance decays and the final state Coulomb interaction. The ratio of the total number of produced $\pi^-$ and $\pi^+$ is used to fit the data. The resulting freeze-out temperature is rather low($T_f < 60$ MeV) with large transverse flow and thus resonance contribution is very small. The difference in the shape of $m_t$ spectra of the oppositely charged pions are found to be due to the Coulomb interaction of the pions.
45880759
Strange matter lumps in the early Universe.
We study the stability of hot strange matter lumps formed in the early Universe. As the Universe cools below the hadronization temperature, these lumps normally become unstable against boiling. They can stabilize themselves against this process if their mass is sufficiently large to hold a hadronic crust by gravitational attraction. Our analysis improves on previous studies of the internal structure of such stable hot quark matter lumps with hadronic crust by correctly treating the constraints from chemical equilibrium of baryonic and electric charge between crust and core. Since the expansion rate of the early Universe is much faster than the cooling rate of the strange matter lumps, their internal structure is characterized by constant entropy per baryon. Our improved analysis confirms the earlier finding that such stable quark matter lumps require a mass well above the total mass inside the horizon.
120021706
TUNNELING WITHOUT BARRIERS
Abstract The evolution of quantum fields in theories with relatively flat potentials is considered. It is shown that bubble nucleation, a quantum mechanical tunneling process, may occur even if V ( φ ) has no barrier. Some implications for inflationary universe scenarios are discussed.
118491865
The CDF dijet excess and Z'cs coupled to the second generation quarks
Recently the CDF collaboration has reported the excess in the dijet invariant-mass distribution of the Wjj events, corresponding to a significance of 3.2 standard deviations. Considering the lack of similar excesses in the $\gamma jj$ and $Z jj$ events yet, we propose a new Z' model: Z' couples only to the second generation quarks. Single production of $\zsc$ as well as associated production with $W,\gamma, Z$ are mainly from the sea quarks. Only $W Z'$ production has additional contribution from one valence quark and one sea quark, which is allowed by CKM mixing. We found that if the new gauge coupling is large enough, marginally permitted by perturbativity, this new model can explain the observed CDF $Wjj$ anomaly as well as the lack of $\gm jj$ and $Z jj$ anomalies. Vanishing coupling of Z'-b-b protects this model from the constraint of p pbar ->WH -> l\nu b \bar{b}.
119342958
Anomalies and effective lagrangians of superconducting cosmic strings
We study the effective lagrangians of superconducting cosmic strings and the underlying anomaly structure leading to various effects. We show that fermionic superconducting cosmic (Nielsen-Olesen) strings arise as a consequence of a mixed anomaly of the form E · B′ where E is the electromagnetic field strength and B′ the core flux of the string. We show how this controls superconductivity, the index theorems, topological mass terms on domain walls, and string-axion interactions. We contrast this to global strinfs with Chern-Simons currents.
123382046
Tunnelling without barriers in curved space-time
Abstract The evolution in curved space-time of quantum fields in theories with relatively flat potentials is considered. It is known that bubble nucleation, a quantum mechanical tunneling process, may occur in flat space-time even if V ( φ ) has no barrier. It is shown that bubble nucleation can also occur in curved space-time even though there is no bounce solution in the standard formalism for the bubble nucleation rate in curved space-time. Some implications for inflationary scenarios are discussed.
119433922
New Precision Electroweak Tests in Supergravity Models
We update the analysis of the precision electroweak tests in terms of four epsilon parameters, e1,2,3,b, to obtain more accurate experimental values of them by taking into account the new LEP data released at the 28th ICHEP (Poland, 1996). We also compute e1 and eb in the context of the no-scale SU(5)×U(1) supergravity model to obtain the updated constraints by imposing the correlated constraints in terms of the experimental ellipses in the e1–eb plane and also by imposing the new conservative bound on the lightest chargino mass, . Upon imposing these new experimental results, we find that the situations in the no-scale model are much more favorable than those in the standard model, and if mt≳ 170 GeV, then the allowed regions at the 95% C.L. in the no-scale model are tan β≳ 4 and for μ>0 (μ< 0), which are in fact much more stringent than in our previous analysis. Therefore, assuming that mt≳ 170 GeV, if the lightest chargino mass bound were to be pushed up to 82 GeV, the sign on the Higgs mixing term μ in the no-scale model could well be determined from the e1–eb constraint to be positive at the 95% C.L. At any rate, better accuracy in the measured mt from the Tevatron in the near future combined with the LEP data is most likely to provide a decisive test of the no-scale SU(5)×U(1) supergravity model.