197 research outputs found
A Partial-Wave Analysis of Centrally Produced Two-Pseudoscalar Final States in pp Reactions at COMPASS
COMPASS is a fixed-target experiment at CERN SPS which focused on light-quark
hadron spectroscopy during the data taking in 2008 and 2009. A world-leading
data set was collected with a 190GeV/c hadron beam impinging on a liquid
hydrogen target in order to study the central production of glueball
candidates.
In this report, we motivate double-Pomeron exchange as a relevant production
process for mesons without valence quark content. We select a centrally
produced sample from the COMPASS data set recorded with a proton beam and
introduce a decomposition into partial waves. Particular attention is paid to
inherent mathematical ambiguities in the amplitude analysis of two-pseudoscalar
final states. Furthermore, we show a simple parametrisation for the centrally
produced K+K- system which can describe the mass dependence of the fit results
with sensible Breit-Wigner parameters.Comment: Proceedings for 51st International Winter Meeting on Nuclear Physics,
21-25 January 2013, Bormio (Italy
The COMPASS Hadron Spectroscopy Programme
COMPASS is a fixed-target experiment at the CERN SPS for the investigation of
the structure and the dynamics of hadrons. The experimental setup features a
large acceptance and high momentum resolution spectrometer including particle
identification and calorimetry and is therefore ideal to access a broad range
of different final states. Following the promising observation of a spin-exotic
resonance during an earlier pilot run, COMPASS focused on light-quark hadron
spectroscopy during the years 2008 and 2009. A data set, world leading in terms
of statistics and resolution, has been collected with a 190GeV/c hadron beam
impinging on either liquid hydrogen or nuclear targets. Spin-exotic meson and
glueball candidates formed in both diffractive dissociation and central
production are presently studied. Since the beam composition includes protons,
the excited baryon spectrum is also accessible. Furthermore, Primakoff
reactions have the potential to determine radiative widths of the resonances
and to probe chiral perturbation theory. An overview of the ongoing analyses
will be presented. In particular, the employed partial wave analysis techniques
will be illustrated and recent results will be shown for a selection of final
states.Comment: 3rd International Conference on Nuclear and Particle Physics with
CEBAF at Jefferson Lab, October 3-8, 2010, Dubrovnik, Croati
Partial-Wave Analysis of the Centrally Produced {\pi}+{\pi}- System in pp Reactions at COMPASS
COMPASS is a fixed-target experiment at CERN SPS which investigates the
structure and spectroscopy of hadrons. During nine weeks in 2008 and 2009, a
190 GeV/c proton beam impinging on a liquid hydrogen target was used in order
to study the production of exotic mesons and glueball candidates at central
rapidities. As no bias on the production mechanism was introduced by the
trigger system, the contribution from diffractive dissociation of the beam
proton poses a challenge. We select a centrally produced sample by kinematic
cuts and introduce a model to describe the data in terms of partial waves.
Preliminary fits are presented, which are consistent with results from previous
experiments. Particular attention is paid to the ambiguities in the amplitude
analysis of the two-pseudoscalar final state.Comment: Sixth International Conference on Quarks and Nuclear Physics, April
16-20, 2012, Ecole Polytechnique, Palaiseau, Paris PoS (QNP2012) 09
Meson spectroscopy with COMPASS
The COMPASS fixed-target experiment at CERN SPS is dedicated to the study of
hadron structure and dynamics. In the physics programme using hadron beams, the
focus is on the detection of new states, in particular the search for
exotic states and glueballs. After a short pilot run in 2004 (190 GeV/c
negative pion beam, lead target), we started our hadron spectroscopy programme
in 2008 by collecting an unprecedented statistics with a negative hadron beam
(190 GeV/c) on a liquid hydrogen target. A similar amount of data with positive
hadron beam (190 GeV/c) has been taken in 2009, as well as some additional data
with negative beam on nuclear targets. The spectrometer features a large
angular acceptance and high momentum resolution and also good coverage by
electromagnetic calorimetry, crucial for the detection of final states
involving or . A first important result is the observation of a
significant spin exotic signal consistent with the disputed
in the pilot run data. This result was recently published. We
present an overview of the status of various ongoing analyses on the 2008/09
data.Comment: 6 pages, 6 figures, to appear in the proceedings of the International
Nuclear Physics Conference 2010, Vancouver, Canada, 04-09 Jul 201
Beam Asymmetry Σ for the Photoproduction of η and ή Mesons at Eγ = 8.8GeV
We report on the measurement of the beam asymmetry Σ for the reactions →γp→pη and →γp→pη′ from the GlueX experiment using an 8.2–8.8-GeV linearly polarized tagged photon beam incident on a liquid hydrogen target in Hall D at Jefferson Laboratory. These measurements are made as a function of momentum transfer −t with significantly higher statistical precision than our earlier η measurements and are the first measurements of η′ in this energy range. We compare the results to theoretical predictions based on t-channel quasiparticle exchange. We also compare the ratio of Ση to Ση′ to these models as this ratio is predicted to be sensitive to the amount of s¯s exchange in the production. We find that photoproduction of both η and η′ is dominated by natural parity exchange with little dependence on −t
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