共查询到20条相似文献,搜索用时 15 毫秒
1.
Hanzhong Zhang Zhongbo Kang Ben-Wei Zhang Enke Wang 《The European Physical Journal C - Particles and Fields》2010,67(3-4):445-454
Using the opacity expansion technique we investigate the photon radiation and dilepton production induced by multiple rescattering as an energetic parton jet passing through the strong interacting medium. The real photon radiation and dilepton invariant-mass spectra of the bremsstrahlung contribution from an energetic quark jet are presented. The leading contribution of total energy loss by photon emission in the medium of a high energetic quark jet is found to be proportional to the jet energy and has a linear dependence on the thickness of the nuclear target. The rescattering contribution to the dilepton production is important only when the pair has a small invariant mass and the jet has relatively low energy. The contribution fraction of the dilepton induced by rescattering in medium is found to be nearly a constant when the ratio of the jet energy to Debye screening mass E/μ is large. 相似文献
2.
Two-photon decays of vector mesons and dilepton decays of scalar mesons which are forbidden in a vacuum and can occur in dense
baryonic matter due to the explicit violation of Lorentz symmetry are described within a quark model of the Nambu-Jona-Lasinio
type. The temperature and chemical potential dependence of these processes is investigated.
Talk at the Helmoltz International Summer School “Dense Matter in Heavy Ion Collision and Astrophysics,” JINR, Dubna, August
21–September 1, 2006.
The text was submitted by the authors in English. 相似文献
3.
《Nuclear Physics A》1997,625(4):832-854
The ω-, ϱ-, and φ-resonance production and their dileptonic decay in π− A reactions at 1.1–1.7 GeV/c are calculated within the intranuclear cascade (INC) approach. The invariant mass distribution of the dilepton pair for each resonance can be decomposed in two components which correspond to their decay “inside” the target nucleus and in the vacuum, respectively. The first components are strongly distorted by the nuclear medium due to resonance-nucleon scattering and a possible mass shift at finite baryon density. These medium modifications are compared to background sources in the dilepton spectrum from πN bremsstrahlung as well as the Dalitz decays of ω and η mesons produced in the reaction. Detailed predictions for π−Pb reactions at 1.3 and 1.7 GeV/c are made within several momentum bins for the lepton pair. 相似文献
4.
E. L. Bratkovskaya 《Acta Physica Hungarica A》2006,27(1):25-33
In this short review the results of detailed studies for dilepton production from p+A andA+A reactions at SIS energies are presented. The calculations are based on a semi-classical BUU transport model that includes the off-shell propagation of vector mesons and evaluates the width of the vector mesons dynamically. Different scenarios of in-medium modifications of vector mesons, such as collisional broadening and dropping vector meson masses, are investigated and the possibilities for an experimental observation of in-medium effects in p+A reactions at 1–4 GeV are discussed for a variety of nuclear targets. 相似文献
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Gy. Wolf 《Acta Physica Hungarica A》1997,5(3):281-297
We present a nonperturbative dynamical study of dilepton and vector meson production in heavy-ion collisions from 1 to 2 GeV/A bombarding energies incorporating all known sources relevant in this energy range. The dynamical evolution of the nucleus-nucleus collision is described by a transport equation of the Boltzmann-Uehling-Uhlenbeck type evolving phase-space distribution functions for nucleons, baryon resonances, pions,η’s,ρ’s andσ’s with their isospin degrees of freedom. We investigate in particular the sensitivity of the calculated yields to predicted changes of theρ andω mesons in dense matter. 相似文献
7.
《Nuclear Physics A》1999,653(3):301-317
We have performed a detailed study of dilepton production from pp collisions including the subthreshold ϱ production via baryonic resonances (N(1520), N(1700)) in addition to the conventional dilepton sources as π0, η, ω and Δ Dalitz decays and direct decays of vector mesons (ϱ, ω). The role of baryonic resonances in ϱ production from nucleon-nucleon collisions is studied in comparison to the DLS data which are well described. 相似文献
8.
In the constituent quark model, a simple mass formula is given to relate the masses of the vector and pseudoscalar mesons. Good agreement is obtained for all mesons, from the lightest π, ? mesons to the heaviest. In the limit of vanishing pion mass, alower limit of 230 MeV is obtained for the constituent quark mass. 相似文献
9.
We calculate the production of large mass dileptons from the passage of jets passing through the quark-gluon plasma. Using the relativistic kinetic theory, we rigorously derive the production rate for the jet-dilepton conversion in the hot medium. The jet-dilepton conversion is compared with the thermal dilepton emission and the Drell-Yan process. The contribution of the jet-dilepton conversion is not prominent for all values of the invariant mass M, and the Drell-Yan process is found to dominate over the thermal dilepton emission and the jet-dilepton conversion for M>2.5 GeV at RHIC. The jet-dilepton conversion is the dominant source of large mass dileptons in the range of 4 GeV<M<10 GeV at LHC. 相似文献
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11.
Ya. V. Burdanov G. V. Efimov S. N. Nedelko S. A. Solunin 《Zeitschrift fur Physik C Particles and Fields》1995,66(1-2):253-261
Masses of the pseudoscalar and vector mesons are calculated within the generalized Nambu-Jona-Lasinio model taking into account homogeneous vacuum gluon field. This vacuum provides an analytical quark confinement. Colorless modes are determined by the confined gluons and are described by the nonlocal quark currents with appropriate radial and angular quantum numbers. An interaction of the quark spin with the vacuum gluon field arises naturally within the model under consideration. It is shown that this spin-field interaction leads to mass splitting between vector and pseudoscalar mesons with identical quark structure (ρ-π,K-K * and so on). This allows to use the four-fermion coupling constant being common for both nonets. 相似文献
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16.
《Nuclear Physics A》1996,611(4):539-567
Dilepton production in proton- and nucleus-induced reactions is studied in the relativistic transport model using initial conditions determined by the string dynamics from RQMD. It is found that both the CERES and HELIOS-3 data for dilepton spectra in proton-nucleus reactions can be well described by the ‘conventional’ mechanism of Dalitz decay and direct vector meson decay. However, to provide a quantitative explanation of the observed dilepton spectra in central S+Au and S+W collisions requires contributions other than these direct decays. Introducing a decrease of vector meson masses in hot and dense medium, we find that these heavy-ion data can also be satisfactorily explained. This agrees with our earlier conclusions based on a fire-cylinder model. We also give predictions for Pb+Au collisions at 160 GeV/nucleon using current CERES mass resolution and acceptance. 相似文献
17.
We describe the chiral symmetric couplings of pions to heavy mesons (B or D), valid in the portion of phase space where the pions have low momentum. In order to include consistently all low energy excitations, the vector mesons (B* or D*) must appear explicitly in the effective lagrangian. The result is then invariant under both the chiral and heavy quark symmetries. We include matrix elements relevant for various weak decays. 相似文献
18.
P. Filip 《Physics of Particles and Nuclei》2014,45(1):7-9
The response of pseudoscalar and vector mesons to strong magnetic fields is studied within a simple constituent quark model using analogy with bound states of Positronium. Magnetic moments of charged vector mesons K*, D*, B* are predicted and it is found that η mesons have magnetic polarizability. In extremely strong magnetic fields, behaviour of J/Ψ mesons is discussed. We speculate on the existence of an induced magnetic moment of η meson. 相似文献
19.
A. Ali A.V. Borisov N.B. Zamorin 《The European Physical Journal C - Particles and Fields》2001,21(1):123-132
We discuss same-sign dilepton production mediated by Majorana neutrinos in high-energy proton–proton collisions for at the LHC energy TeV, and in the rare decays of the , and B mesons of the type . For the pp reaction, assuming one heavy Majorana neutrino of mass , we present discovery limits in the plane where are the mixing parameters. Taking into account the present limits from low-energy experiments, we show that at LHC one has
sensitivity to heavy Majorana neutrinos up to a mass TeV in the dilepton channels , and , but the dilepton states will not be detectable due to the already existing constraints from neutrinoless double beta decay. We work out a large number
of rare meson decays, both for the light and heavy Majorana neutrino scenarios, and argue that the present experimental bounds
on the branching ratios are too weak to set reasonable limits on the effective Majorana masses.
Received: 24 April 2001 / Published online: 29 June 2001 相似文献
20.
《Nuclear Physics A》1997,614(4):552-564
From the full stopping scenario, the dilepton production in a baryon-rich quark-gluon fireball has been studied based on a relativistic hydrodynamic model. Due to the influence of the phase boundary on the evolution of the system, the quark phase gives the dominant contribution to the dilepton spectrum. In particular, with increasing initial baryon density, the total dilepton yield first rapidly rises when the initial hadronic system goes to the initial quark system, then goes down owing to the suppression of the dilepton production, thus making a characteristic peak signaling the formation of the baryon-rich quark-gluon matter which appears in the total yield. These characteristics can be tested in future experiments at CERN and Brookhaven. 相似文献