49 research outputs found
Rho-Omega Mixing and the Pion Form Factor in the Time-like Region
We determine the magnitude, phase, and -dependence of -
``mixing'' in the pion form factor in the time-like region through fits to
e^+e^- \ra \pi^+ \pi^- data. The associated systematic errors in these
quantities, arising from the functional form used to fit the resonance,
are small. The systematic errors in the mass and width, however, are
larger than previously estimated.Comment: 20 pages, REVTeX, epsfig, 2 ps figures, minor change
Enhanced J/psi suppression due to gluon depletion
The nonlinear effect of gluon depletion in the collision of large nuclei can
be large. It is due to multiple scatterings among comoving partons initiated by
primary scattering of partons in the colliding nuclei. The effect can give rise
to substantial suppression of production in very large nuclei, even if
the linear depletion effect is insignificant for the collisions of nuclei of
smaller sizes. This mechanism offers a natural explanation of the enhanced
suppression in the Pb-Pb data recently observed by NA50.Comment: 6 pages + 2 figures (in ps file), LaTex, submitted to Phys. Rev. Let
Mass and width of sigma(750) scalar meson from measurements of piN->pi(-)pi(+)N on polarized targets
The measurements of reactions at 17.2
GeV/c and at 5.98 and 11.85 GeV/c made at
CERN with polarized targets provide a model-independent and
solution-independent evidence for a narrow scalar state sigma(750). The
original chi^2 minimization method and the recent Monte Carlo method for
amplitude analysis of data at 17.2 GeV/c are in excellent agreement. Both
methods find that the mass distribution of the measured amplitude with recoil transversity ``up'' resonates near 750 MeV while the
amplitude with recoil transversity ``down'' is large and
nonresonating. The amplitude contributes as a strong background
to S-wave intensity I_S = (|S|^2 + |\overline S |^2)\Sigma\sigmaI_S|\overline S |^2\Sigmatm_\sigma = 753 \pm 19\Gamma_\sigma = 108 \pm 53\sigma(750)\sigma(750)\gamma\gamma \to \pi\pi\pi\pi$ phase shifts .Comment: 77 page
Factorization in the model of unstable particles with continuous masses
We study processes with unstable particles in intermediate time-like states.
It is shown that the amplitudes squared of such processes factor exactly in the
framework of the model of unstable particles with continuous masses. Decay
widths and cross sections can then be represented in a universal factorized
form for an arbitrary set of interacting particles. This exact factorization is
caused by specific structure of propagators in the model. We formulate the
factorization method and perform a phenomenological analysis of the
factorization effects. The factorization method considerably simplifies
calculations while leading to compact and reasonable results.Comment: 20 pages, 6 figure
ALICE: Physics Performance Report, Volume I
ALICE is a general-purpose heavy-ion experiment designed to study the physics of strongly interacting matter and the quark-gluon plasma in nucleus-nucleus collisions at the LHC. It currently includes more than 900 physicists and senior engineers, from both nuclear and high-energy physics, from about 80 institutions in 28 countries. The experiment was approved in February 1997. The detailed design of the different detector systems has been laid down in a number of Technical Design Reports issued between mid-1998 and the end of 2001 and construction has started for most detectors. Since the last comprehensive information on detector and physics performance was published in the ALICE Technical Proposal in 1996, the detector as well as simulation, reconstruction and analysis software have undergone significant development. The Physics Performance Report (PPR) will give an updated and comprehensive summary of the current status and performance of the various ALICE subsystems, including updates to the Technical Design Reports, where appropriate, as well as a description of systems which have not been published in a Technical Design Report. The PPR will be published in two volumes. The current Volume I contains: 1. a short theoretical overview and an extensive reference list concerning the physics topics of interest to ALICE, 2. relevant experimental conditions at the LHC, 3. a short summary and update of the subsystem designs, and 4. a description of the offline framework and Monte Carlo generators. Volume II, which will be published separately, will contain detailed simulations of combined detector performance, event reconstruction, and analysis of a representative sample of relevant physics observables from global event characteristics to hard processes