109 research outputs found
Highlights from the COMPASS experiment at CERN -- Hadron spectroscopy and excitations
The COMPASS experiment at the CERN-SPS studies the spectrum and the structure
of hadrons by scattering high energy hadrons and polarised muons off various
fixed targets. Recent results for the hadron programme comprise highlights from
different topics. A selective overview is given and, among others, the
following results are discussed. The precise determination of the pion
polarisability, a long standing puzzle that has been solved now, is presented
as well as measurements of radiative widths. The observation of a new narrow
axial-vector state, the , as well as deeper insights into the exotic
-wave, which is under study since decades by several experiments, are
discussed and further, the search for the charmonium-like exotic
state in the COMPASS data is covered.Comment: 12 pages, 23 figures, ICNFP2015 Conference Proceedings, to appear in
the proceedings of the 4th International Conference on New Frontiers in
Physics, Creta, Greece, August 23-20, 201
Diffractive pion production at COMPASS -- First results on 3 final states - neutral mode
The COMPASS experiment at CERN is designed for light hadron spectroscopy with
emphasis on the detection of new states, in particular the search for exotic
states and glue-balls. After a short pilot run in 2004 (190 GeV/c negative pion
beam, lead target) showing significant production strength for an exotic
state at 1.66\,GeV/, we have collected data with a
190 GeV/c negative charged hadron beam on a proton (liquid hydrogen) and
nuclear targets in 2008 and 2009. The spectrometer features good coverage by
electromagnetic calorimetry, and our data provide excellent opportunity for
simultaneous observation of new states in two different decay modes in the same
experiment. The diffractively produced system for example can be
studied in both modes and
. Charged and neutral mode rely
on completely different parts of the spectrometer. Observing a new state in
both modes provides important cross-check. First results of a preliminary PWA
performed on the 2008 data are presented.Comment: 7 pages, 7 figures, to appear in the AIP Conf. Proc., Hadron 2009,
XIII Intern. Conference on Hadron Spectroscopy, Nov 29th - Dec 4th 2009,
Florida State Universit
New results on the search for spin-exotic mesons with COMPASS
The COMPASS fixed-target experiment at the CERN-SPS studies the structure and
spectrum of hadrons. One important goal using hadron beams is the search for
new states, in particular spin-exotic mesons and glueballs. As a first input to
the puzzle, COMPASS observed a significant spin-exotic signal in the
2004 pilot run data (190\,GeV/ beam, Pb target) in three charged
pion final states consistent with the disputed . We started our
hadron spectroscopy programme in 2008 by collecting very high statistics using
a 190 GeV/ negative pion beam scattered off a liquid hydrogen (proton)
target. The current status and new results from the 2008 data on the search for
the resonance with exotic quantum numbers
obtained from partial-wave analyses of the and decay
channels are presented.Comment: 6 pages, 5 figures, HEP 2011 Conference Proceedings, to appear in the
proceedings of the XXI International Europhysics Conference on High Energy
Physics: HEP 2011, Grenoble, France, 21-27 July 2011; v2: Corrected typos,
added a referenc
First Results on Hadron Spectroscopy at COMPASS
The COMPASS fixed-target experiment at the CERN SPS is dedicated to the study
of hadron structure and dynamics. One goal of the physics programme using
hadron beams is the search for new states, in particular the search for
exotic states and glueballs. After a short pilot run in 2004 (190
GeV/c beam, lead target), we started our hadron spectroscopy
programme in 2008 by collecting unprecedented statistics using 190 GeV/c
negative hadron beams on a liquid hydrogen target. A similar amount of data
with 190 GeV/c positive hadron beams has been taken in 2009, as well as some
data (negative beam) on nuclear targets. As a first result the observation of a
significant spin-exotic signal in the 2004 data -- consistent with the
disputed -- was recently published. Our spectrometer features
good coverage by electromagnetic calorimetry, crucial for the detection of
final states involving , or , and the 2008/09 data provide
an excellent opportunity for the simultaneous observation of new states in
different decay modes. The diffractively produced system for
example can be studied in and
final states, respectively. Observation of new states in both modes provides
important consistency checks within the same experiment as the reconstruction
of charged and neutral modes rely on completely different parts of the
apparatus. We present the first results and give an overview of the status on
various ongoing analyses of the 2008/09 data.Comment: 6 pages, 5 figures, to appear in the proceedings of the 35th
Conference on High Energy Physics 2010, Paris, France, 22-28 Jul 201
COMPASS Hadron Spectroscopy -- Final states involving neutrals and kaons
The COMPASS experiment at CERN is well designed for light-hadron spectroscopy
with emphasis on the detection of new states, in particular the search for
-exotic states and glueballs. We have collected data with 190 GeV/c
charged hadron beams on a liquid hydrogen and nuclear targets in 2008/09. The
spectrometer features good coverage by electromagnetic calorimetry and a RICH
detector further provides / separation, allowing for studying final
states involving neutral particles like or as well as hidden
strangeness, respectively. We discuss the status of ongoing analyses with
specific focus on diffractively produced as well as
final states.Comment: 3 pages, 4 figures, Conf. Proc., to appear in the Intern. Journal of
Modern Phys. A, 11th Intern. Workshop on Meson Production, Properties and
Interaction, KRAK\'OW, POLAND, 10-15 June 201
Diffractive dissociation into final states
The COMPASS fixed-target experiment at CERN/SPS is dedicated to the study of
hadron structure and spectroscopy, especially the search for spin-exotic
states. After having started to study the existence of the spin-exotic
resonance in the 2004 pilot-run data, the new 2008/09 data will
enable us to further clarify the situation. Apart from the
resonance, also a spin-exotic was reported in the past in the
decay channel by the E852/BNL experiment, however, this state
still lacks confirmation. We present a first event selection of the
diffractively produced system showing clean
and resonances at competing statistics. A partial-wave analysis
started on and decay channels will further
complete the search for spin-exotics in the 2008/09 COMPASS data.Comment: 4 pages, 6 figures, Hadron2011 Conference Proceedings, to appear in
the proceedings of the XIV International Conference on Hadron Spectroscopy:
Hadron 2011, Munich, Germany, 13-17 June 201
Spin-exotic search in the decay channel: New results on in comparison to final states (diffractively produced on proton)
The COMPASS experiment at CERN SPS features charged particle tracking as well
as good coverage by electromagnetic calorimetry, and our data provide an
excellent opportunity for simultaneous observation of new states in different
decay modes by the same experiment. The existence of the spin-exotic
resonance in the decay channel is studied for the first
time at COMPASS in both decay modes of the diffractively produced
system: and . A preliminary partial-wave analysis
performed on the 2008 proton target data allows for a first conclusive
comparison of both decay modes not only for main waves but also
for small ones. We find the neutral versus charged mode results in excellent
agreement with expectations from isospin symmetry. Both, the intensities and
the relative phases to well-known resonances, are consistent for the neutral
and the charged decay modes of the system. The status on the
search for the spin-exotic resonance produced on a proton target
is discussed.Comment: 6 pages, 16 figures, Hadron2011 Conference Proceedings, to appear in
the proceedings of the XIV International Conference on Hadron Spectroscopy:
Hadron 2011, Munich, Germany, 13-17 June 201
COMPASS Hadron Spectroscopy - Final states involving neutrals and kaons
The COMPASS experiment at CERN is well designed for light-hadron spectroscopy with emphasis on the detection of new states, in particular the search for J P C -exotic states and glueballs. We have collected data with 190 GeV/c charged hadron beams on a liquid hydrogen and nuclear targets in 2008/09. The spectrometer features good coverage by electromagnetic calorimetry and a RICH detector further provides π / K separation, allowing for studying final states involving neutral particles like π 0 or η as well as hidden strangeness, respectively. We discuss the status of ongoing analyses with specific focus on diffractively produced (π 0 π 0 π) − as well as (KKπ) − final states
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
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