117796529
Initial Parton Distribution just after Heavy-Ion Collisions
We study in detail the initial distribution of a parton system that is formed just after relativistic heavy-ion collisions by elastic scattering among the constituent partons and analyze the baryon and strangeness contents of the primary parton system. We present the rapidity and the energy distributions of the system.
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.
124365920
A statistical model analysis of the rapidity distribution of hadrons
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.
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.
122366381
Collective flow model for the pion transverse momentum spectra from relativistic nuclear collisions at CERN
The transverse momentum spectra for pions observed by WA80 and NA35 collaborations are analysed within a fireball model with collective isentropic expansion and a realistic freeze-out criterion. By varing the initial state of the fireball, an excellent fit to the data is achieved for the whole measured range ofPT. Slight differences in the data for the spectral slopes from central and pheripheral collisions originate in our model from the difference in the size of the fireball and in the number of participating nucleons in central and peripheral collisions. Using additional information from two-pion correlations, we can extrapolate our model back from the freeze-out point (determined from the spectra) to the initial state; we find that an initial energy density of 1.5–2GGeV/fm3 is sufficient to explain the data from central O+Au collisions at 200A GeV.
118524475
$B_d$ - $\bar{B}_d$ mixing versus $B_s$ - $\bar{B}_s$ mixing with the anomalous $Wtb$ couplings
We explore the effects of the anomalous $tbW$ couplings on the $\bd$ mixing and recently measured $\bs$ mixing. The combined analysis of mixings via box diagrams with penguin decays provides strong constraints on the anomalous top quark couplings. We find the bound from the $\bd$ mixing data is stronger than that from the $\bs$ mixing.
16963420
Evolution equation for the heavy quark distribution function in the parton model approach
We explore the perturbative QCD corrections to the inclusive semileptonic decays of $B$ mesons. In inclusive $B$ decay processes the parton picture works well and the scaling feature manifests because the mass of $b$ quark is larger than the QCD scale. Due to this property, the decay rate may be expressed by a single structure function describing the light-cone distribution of $b$ quark apart from the kinematic factor. We derive a $q^2$ evolution equation for the distribution function, which violates the scaling property through the Altarelli-Parisi type approach. The evolution equation is numerically solved and its phenomenological implications are also discussed.
8269651
Neutralino dark matter in mirage mediation
We study the phenomenology of neutralino dark matter (DM) in a mirage mediation scenario of supersymmetry breaking which results from the moduli stabilization in some string/brane models. Depending upon the model parameters, especially the anomaly to modulus mediation ratio determined by the moduli stabilization mechanism, the nature of the lightest supersymmetric particle (LSP) changes from bino-like neutralino to Higgsino-like neutralino via a bino–Higgsino mixing region. For the bino-like LSP, the standard thermal production mechanism can give the right amount of relic DM density through the stop/stau–neutralino coannihilation or the pseudoscalar Higgs resonance process. We also examine the prospect of direct and indirect DM detection in various parameter regions of mirage mediation. Neutralino DM in the galactic halo might be detected by near future direct detection experiments in the case of the bino–Higgsino mixed LSP. The gamma ray flux from the galactic centre might be detectable also if the DM density profile takes a cuspy shape.
118645218
Incorporation of fermions into double field theory
A bstractBased on the stringy differential geometry we proposed earlier, we incorporate fermions such as gravitino and dilatino into double field theory in a manifestly covariant manner with regard to O(D, D) T-duality, diffeomorphism, one-form gauge symmetry for B-field and a pair of local Lorentz symmetries. We note that there are two kinds of fermions in double field theory: O(D, D) singlet and non-singlet which may be identified, respectively as the common and the non-common fermionic sectors in type IIA and IIB suergravities. For each kind, we construct corresponding covariant Dirac operators. Further, we derive a simple criterion for an O(D, D) rotation to flip the chirality of the O(D, D) non-singlet chiral fermions, which implies the exchange of type IIA and IIB supergravities.
119916631
Charge violation by instantons in Chern-Simons theories☆
Abstract We study the effect of magnetic monopole instantons in abelian Chern-Simons gauge theories. An effective interaction induced by instantons is shown to break the global part if U(1) gauge symmetry into a finite cyclic subgroup. We present an understanding of the complex action and solution in euclidean space-time, boundary terms, and linear divergence of the instanton action.