336 research outputs found
Masses and Internal Structure of Mesons in the String Quark Model
The relativistic quantum string quark model, proposed earlier, is applied to
all mesons, from pion to , lying on the leading Regge trajectories
(i.e., to the lowest radial excitations in terms of the potential quark
models). The model describes the meson mass spectrum, and comparison with
measured meson masses allows one to determine the parameters of the model:
current quark masses, universal string tension, and phenomenological constants
describing nonstring short-range interaction. The meson Regge trajectories are
in general nonlinear; practically linear are only trajectories for light-quark
mesons with non-zero lowest spins. The model predicts masses of many new
higher-spin mesons. A new meson is predicted with mass 1910 Mev. In
some cases the masses of new low-spin mesons are predicted by extrapolation of
the phenomenological short-range parameters in the quark masses. In this way
the model predicts the mass of to be MeV, and
the mass of to be MeV (the potential model predictions
are 100 Mev lower). The relativistic wave functions of the composite mesons
allow one to calculate the energy and spin structure of mesons. The average
quark-spin projections in polarized -meson are twice as small as the
nonrelativistic quark model predictions. The spin structure of reveals an
80% violation of the flavour SU(3). These results may be relevant to
understanding the ``spin crises'' for nucleons.Comment: 30 pages, REVTEX, 6 table
A study of the pi^0pi^0 system produced in charge exchange and central collisions
A study of the system produced in charge exchange
collisions at 38 and 100 GeV/c and in central interactions at 450 GeV/c
has been carried out. The wave has rather a complicated structure in both
processes indicating the existence of several scalar resonances. The
and appear as dips at 1 and 1.5 GeV in the wave for charge
exchange reaction, and as shoulders at these masses in the wave for central
production. The production of the , and in
the reaction as a function of the
kinematical filter shows the behaviour differed from what has been observed for
the undisputed mesons. An extra state is seen in the
wave for charge exchange reaction as a dip at 2 GeV. Resonances with higher
spins, , and , have also been studied. All
the three mesons are produced in the reaction mainly
via an one-pion exchange for small , whereas a natural-parity exchange
domimates for large . The behaviour of the centrally produced
as a function of the is consistent with what has been observed for
other states.Comment: 6 pages, 6 figures, use file stwol.sty, presented at International
High-Energy Physics Euroconference in Quantum Chromodynamics, 2-8 July 1998,
Montpellier, France on behalf of the GAMS and WA102 Collaboration
Proposed Search for Mixing in Polarization Phenomena
The and meson mass difference induces the mixing of the
and resonances, the amplitude of which, between the
and thresholds, is large in magnitude, of the order of , and possesses the
phase sharply varying by about 90. We suggest performing the polarized
target experiments on the reaction at high energy in
which the fact of the existence of mixing can be
unambiguously and very easily established through the presence of a strong jump
in the azimuthal asymmetry of the wave production cross section
near the thresholds. The presented estimates of the polarization
effect to be expected in experiment are to a great extent model independent.Comment: RevTeX, 9 pages, 1 figure. A number of typographical and grammatical
errors correcte
Amplitude analysis of reactions pi(-)p->etapi(-)p and pi(-)p->etapi(0)n on polarized target and the exotic 1-+ meson
Recently several experimental groups analysed data on and reactions with exotic -wave and
found a conflicting evidence for an exotic meson . High
statistics data on these reactions are presently analysed by BNL E852
Collaboration. All these analyses are based on the crucial assumption that the
production amplitudes do not depend on nucleon spin. This assumption is in
sharp conflict with the results of measurements of ,
and on polarized targets at
CERN which find a strong dependence of production amplitudes on nucleon spin.
To ascertain the existence of exotic meson , it is necessary to
perform a model-independent amplitude analysis of reactions and . We demonstrate that measurements of
these reactions on transversely polarized targets enable the required model
independent amplitude analysis without the assumption that production
amplitudes are independent on nucleon spin. We suggest that high statistics
measurements of reactions and be made on polarized targets at BNL and at Protvino IHEP, and that
model-independent amplitude analyses of this polarized data be performed to
advance hadron spectroscopy on the level of spin dependent production
amplitudes.Comment: 23 page
Meson model for f_0(980) production in peripheral pion-nucleon reactions
The Juelich model for pion-pion-scattering, based on an effective meson-meson
Lagrangian is applied to the analysis of the S-wave production amplitudes
derived from the BNL E852 experiment pi^- p -> pi^0 pi^0 n for a pion momentum
of 18.3 GeV. The unexpected strong dependence of the S-wave partial wave
amplitude on the momentum transfer between the proton and neutron in the
vicinity of the f_0(980) resonance is explained in our analysis as interference
effect between the correlated and uncorrelated pi^0 pi^0 pairs.Comment: 6 pages, 7 figures, formulas added, typos removed, new figure
EPS09 - Nuclear PDFs and Their Uncertainties at NLO
In this talk, we present our recent next-to-leading order (NLO) nuclear
parton distribution functions (nPDFs), which we call EPS09. As an extension to
earlier NLO analyses, we supplement the deep inelastic scattering and Drell-Yan
dilepton data by inclusive midrapidity pion measurements from RHIC in order to
reduce the otherwize large freedom in the nuclear gluon densities. Our
Hessian-type error analysis leading to a collection of nPDF error sets, is the
first of its kind among the nPDF analyses.Comment: 4 pages, 4 figures - To appear in the conference proceedings for
Quark Matter 2009, March 30 - April 4, Knoxville, Tennesse
Partial wave analysiss of pbar-p -> piminus-piplus, pizero-pizero, eta-eta and eta-etaprime
A partial wave analysis is presented of Crystal Barrel data on pbar-p ->
pizero-pizero, eta-eta and eta-etaprime from 600 to 1940 MeV/c, combined with
earlier data on d\sigma /d\Omega and P for pbar-p->piminus-piplus. The
following s-channel I=0 resonances are identified: (i) J^{PC} = 5^{--} with
mass and width (M,\Gamma) at (2295+-30,235^{+65}_{-40}) MeV, (ii) J^{PC} =
4^{++} at (2020+-12, 170+-15) MeV and (2300+-25, 270+-50) MeV, (iii) 3D3 JPC =
3^{--} at (1960+-15, 150+-25) MeV and (2210+-4$, 360+-55) MeV, and a 3G3 state
at (2300 ^{+50}_{-80}, 340+-150) MeV, (iv) JPC = 2^{++} at (1910+-30, 260+-40)
MeV, (2020+-30, 275+-35) MeV, (2230+-30, 245+-45) MeV, and (2300+-35, 290+-50)
MeV, (v) JPC = 1^{--} at (2005+-40, 275+-75) MeV, and (2165+-40, 160
^{+140}_{-70}) MeV, and (vi) JPC = 0^{++} at (2005+-30, 305+-50) MeV,
(2105+-15, 200+-25) MeV, and (2320+-30, 175+-45) MeV. In addition, there is a
less well defined 6^{++} resonance at 2485+-40 MeV, with Gamma = 410+-90 MeV.
For every JP, almost all these resonances lie on well defined linear
trajectories of mass squared v. excitation number. The slope is 1.10+-0.03
Gev^2 per excitation. The f_0(2105) has strong coupling to eta-\eta, but much
weaker coupling to pizero-pizero. Its flavour mixing angle between q-qbar and
s-sbar is (59-71.6)deg, i.e. dominant decays to s-sbar. Such decays and its
strong production in pbar-p interactions strongly suggest exotic character.Comment: Makes available the combined fit to Crystal Barrel data on pbar-p ->
2-body final states. 29 pages, 11 figures. Typo corrected in version
The two-pion spectra for the reaction \pi^- p -> \pi^0\pi^0 n at 38 GeV/c pion momentum and combined analysis of the GAMS, Crystal Barrel and BNL data
We perform the K-matrix analysis of meson partial waves with IJ^{PC}
=00^{++}, 10^{++}, 02^{++}, 12^{++} basing on GAMS data on \pi^-p -> \pi^0\pi^0
n, \eta\eta n, \eta\eta' n together with BNL data on \pi^-p -> K\bar K n and
Crystal Barrel data on p\bar p (at rest) -> \pi^0\pi^0\pi^0, \pi^0\eta\eta,
\pi^0\pi^0\eta. The positions of the amplitude poles (physical resonances) are
determined as well as the positions of the K-matrix poles (bare states) and the
values of bare state couplings to two-meson channels. Nonet classification of
the determined bare states is discussed.Comment: LaTex, 15 pages and 10 figure
Screening and Anti-Screening Effects in J/psi Production on Nuclei
The nuclear effects in J/psi hadro- and electroproduction on nuclei are
considered in framework of reggeon approach. It is shown that screening regime
which holds for electroproduction at x_F > 0.7 and for hadroproduction at x_F >
-(0.3-0.4) is changed with anti-screening regime for smaller x_F values.Comment: 6 pages, 6 figures. Small changes in wordin
Transverse Radial Flow Effects on Two- and Three-Particle Angular Correlations
We use a simple a transverse radial boost scenario coupled to PYTHIA events
to illustrate the impact radial flow may have on two- and three-particle
correlation functions measured in heavy-ion collisions. We show that modest
radial velocities can impart strong modifications to the correlation functions,
some of which may be interpreted as same side ridge and away side structure
that can mimic conical emission.Comment: 7 figures, 9 pages, Material presented in part by Pruneau at HOC 07,
Montreal, Canada Accepted for publication in Nucl Phys A (Jan 2008
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