5,496 research outputs found
Resonances, and mechanisms of Theta-production
After explaining necessity of exotic hadrons, we discuss mechanisms which
could determine production of the exotic Theta-baryon. A possible important
role of resonances (producing the Theta in real or virtual decays) is
emphasized for various processes. Several experimental directions for studies
of such resonances, and the Theta itself, are suggested. We briefly discuss
also recent negative results on the Theta-baryon.Comment: 6 page
Extracting W Boson Couplings from the Production of Four Leptons
We consider the processes , including all possible charged lepton combinations, with
regard to measuring parameters characterizing the boson. We calculate at
what level these processes can be used to measure anamolous triple-boson
vertice coupling parameters for the cases of colliders at 500
and 1 center of mass energies.Comment: 13 pages,OCIP/C-93-
The A Dependence of Open Charm and Bottom Production
We study inclusive heavy quark and exclusive heavy quark pair production in
pp, pA and AA interactions. Intrinsic transverse momentum is introduced in pp
interactions. Nuclear effects, limited to broadening and nuclear
shadowing, are introduced in pA and AA interactions. The nuclear dependence is
studied over a range of energies, both in fixed target and collider setups.Comment: 69 pages, 42 .eps figures, to appear in the Proceedings of the Hard
Probe Collaboratio
Measuring hadron properties at finite temperature
We estimate the numbers and mass spectra of observed lepton and kaon pairs
produced from meson decays in the central rapidity region of an Au+Au
collision at lab energy 11.6 GeV/nucleon. The following effects are considered:
possible mass shifts, thermal broadening due to collisions with hadronic
resonances, and superheating of the resonance gas. Changes in the dilepton mass
spectrum may be seen, but changes in the dikaon spectrum are too small to be
detectable.Comment: 9 pages (revtex), 3 figures (uuencoded postscript
K*(892)0 Production in Relativistic Heavy Ion Collisions at sqrt(s_NN) = 130 GeV
Preliminary results on the K*(892)0 -> pi + K production using the
mixed-event technique are presented. The measurements are performed at
mid-rapidity by the STAR detector in sqrt(s_NN) = 130 GeV Au-Au collisions at
RHIC. The K*0 to negative hadron, kaon and phi ratios are obtained and compared
to the measurements in e+e-, pp and pbarp at various energies.Comment: 8 pages, 3 figures, proceedings of Strange Quarks in Matter
(SQM2001), Frankfurt am Main, Germany, to be published in J. Phys.
On photoexcitation of baryon antidecuplet
We show that the photoexcitation of the baryon antidecuplet, suggested by the
soliton classification of low-lying baryons, is strongly suppressed on the
proton target. The process occurs mostly on the neutron target. This
qualitative prediction can be useful in identifying the non-exotic members of
the antidecuplet in the known baryon spectrum. We also analyze the
interrelation between photocouplings of various baryon multiplets in the
soliton picture and in the nonrelativistic quark model.Comment: 9 pages, one Latex figur
Lifetimes of Heavy-Flavour Hadrons -- Whence and Whither?
A theoretical treatment for the weak decays of heavy-flavour hadrons has been
developed that is genuinely based on QCD. Its methodology as it applies to
total lifetimes and the underlying theoretical issues are sketched. Predictions
are compared with present data. One discrepancy emerges: the beauty baryon
lifetime appears to be significantly shorter than expected. The ramifications
of those findings are analyzed in detail.Comment: 15 pages, no figures, LATEX, two references added and new information
concerning a lower charm content in B decays incorporate
Open and hidden charm in proton-nucleus and heavy-ion collisions
We review the collectivity and the suppression pattern of charmed mesons -
produced in proton-nucleus and nucleus-nucleus collisions at SPS (158 AGeV) and
RHIC energies (21 ATeV) - in comparison to dynamical and thermal models. In
particular, we examine the charmonium `melting' and the `comover dissociation'
scenarios - implemented in a microscopic transport approach - in comparison to
the available data from the SPS and RHIC. The analysis shows that the dynamics
of c, c-bar quarks at RHIC are dominated by partonic or `pre-hadronic'
interactions in the strongly coupled plasma stage. Both the `charmonium
melting' and the hadronic `comover absorption and recreation model' are found,
however, to be compatible with the experimental observation at SPS energies;
the experimental ratio of Psi'/J/Psi versus centrality clearly favors the
`hadronic comover' scenario. We find that the collective flow of charm in the
purely hadronic Hadron-String Dynamics (HSD) transport appears compatible with
the data at SPS energies, but substantially underestimates the data at top RHIC
energies. Thus, the large elliptic flow v2 of D-mesons and the low R_AA(p_T) of
J/Psi seen experimentally have to be attributed to early interactions of
non-hadronic degrees of freedom. Simultaneously, we observe that non-hadronic
interactions are mandatory in order to describe the narrowing of the J/Psi
rapidity distribution from pp to central Au+Au collisions at the top RHIC
energy. We demonstrate additionally that the strong quenching of low-pT J/Psi's
in central Au+Au collisions indicates that a large fraction of final J/Psi
mesons is created by a coalescence mechanism close to the phase boundary.
Throughout this review we, furthermore, provide predictions for charm
observables from Au+Au collisions at FAIR energies of 25-35 AGeV.Comment: review for Int. J. Mod. Phys. E, 75 pages, 50 figure
A possible explanation why the Theta+ is seen in some experiments and not in others
To understand the whole set of positive and null data on the
Theta+(1530)-production, we suggest the hypothesis that multiquark hadrons are
mainly generated from many-quark states, which emerge either as short-term
hadron fluctuations, or as hadron remnants in hard processes. This approach
allows us to describe both non-observation of the Theta+ in current null
experiments and peculiar features of its production in positive experiments.
Further, we are able to propose new experiments that might be decisive for the
problem of the Theta+ existence. Distributions of the Theta+ in such
experiments can give important information both on higher Fock components of
conventional hadrons and about structure and hadronization properties of hadron
remnants produced in hard processes. We also explain that description of
multiquark hadrons may require a modified form of the constituent quark model,
with quark masses and couplings being intermediate between their values for the
familiar constituent quarks and the current ones.Comment: 18 pages. Some changes in the text; experimental suggestions
collected in a special subsection, references added and refreshe
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