Chiral Symmetry in Charmonium - Pion Cross Section

We perform a non-perturbative calculation of the $J/\Psi-\pi$ cross section using a $SU(2)\times SU(2)$ effective Lagrangian. Our results differ from those of previous calculations, specially in the description of vertices involving pions.Comment: 6 pages, RevTeX including 2 figures in eps file

Update on the use of cardiac markers in the diagnosis of acute coronary syndrome

AbstractAccurate identification of the cause of chest pain is a challenge to the emergency physician because a significant proportion of patients with acute coronary syndrome (ACS) present atypically. Cardiac troponins are the most sensitive and specific biochemical markers of myocardial damage, and are an important diagnostic tool in the evaluation of ACS. High-sensitivity troponins (hsTn) have been introduced in recent years, and have been shown to have increased accuracy in the diagnosis of acute myocardial infarction (AMI), both at presentation and upon early onset of chest pain. A combination of hsTn readings at presentation and at either 2 hours or 3 hours after the onset of symptoms increases the sensitivity of diagnosing AMI as compared to at presentation alone, and this combination may negate the need for other cardiac markers. The absolute change in hsTn 2 hours after presentation was also found to be useful in the diagnosis of AMI, but not the relative change. However, hsTn has lower specificity in comparison with traditional troponin, and its levels may be elevated even in certain non-ACS settings. The interpretation of troponin values in patients with chronic renal failure must also be done with caution, as their baseline may be elevated, even in the absence of an acute event. Given these pitfalls, the assessment of ACS must still be global, comprising clinical history, electrocardiogram changes, troponin increase, and/or a new wall-motion abnormality on echocardiogram or nuclear scan showing new loss of viable myocardium. High-sensitivity troponin also has a potential use in prognosticating atherosclerotic disease in chronic renal patients as well as population screening of cardiovascular risk factors, although these uses have not been well studied. Identification of patients with unstable angina without myocardial infarction also remains a challenge, as the sensitivity of cardiac troponin in this area remains moderate to low. However, new cardiac markers such as copeptin, ischemia-modified albumin, and heart-type acid binding protein, are still being studied and provide a window of hope in the diagnosis of unstable angina

Charm meson scattering cross sections by pion and rho meson

Using the local flavor SU(4) gauge invariance in the limit of vanishing vector meson masses, we extend our previous study of charm meson scattering cross sections by pion and rho meson, which is based only on the pseudoscalar-pseudoscalar-vector meson couplings, to include also contributions from the couplings among three vector mesons and among four particles. We find that diagrams with light meson exchanges usually dominate the cross sections. For the processes considered previously, the additional interactions lead only to diagrams involving charm meson exchanges and contact interactions, and the cross sections for these processes are thus not much affected. Nevertheless, these additional interactions introduce new processes with light meson exchanges and increase significantly the total scattering cross sections of charm mesons by pion and rho meson.Comment: 14 pages, revtex, 6 figures, added a figure on the effects of on-shell divergence, final version to appear in Nucl. Phys.

Enhancement of Intermediate Mass Dileptons From Charm Decays At SPS Energies

We study the dimuon yield from open charm decays in the intermediate mass region(IMR) in heavy-ion collisions at the CERN-SPS energy. We find that final state rescatterings which broaden the $m_T$ spectrum of charmed mesons can enrich the part of the phase space covered by the NA50 experiment, thus leading to an apparent enhancement of IMR dileptons within the acceptance of the experiment. Such an enhancement increases with the dimuon invariant mass and the single muon energy cut-off.Comment: Revtex, 16 pages including 6 eps figures, using epsf.st