Bulletin of the American Physical Society
2005 2nd Joint Meeting of the Nuclear Physics Divisions of the APS and The Physical Society of Japan
Sunday–Thursday, September 18–22, 2005; Maui, Hawaii
Session 1WD: Workshop 4A: Beyond qq-bar and qqq: Pentaquarks and More |
Hide Abstracts |
Sponsoring Units: DNP JPS Chair: Wolfgang Lorenzon, University of Michigan Room: Ritz-Carlton Hotel Salon 1 |
Sunday, September 18, 2005 9:00AM - 9:30AM |
1WD.00001: Pentaquarks: An Overview of Experimental Results Invited Speaker: During the past few years numerous experiments have searched for, and possibly found, evidence for pentaquarks. The experiments have covered a wide range of beam energies, different types of beam particles, and target materials. The evidence that supports the discovery of pentaquarks has been challenged by experimental data in which there is no evidence for pentaquarks. It is in this context that recent results in the search for pentaquarks will be reviewed. [Preview Abstract] |
Sunday, September 18, 2005 9:30AM - 10:00AM |
1WD.00002: Search for pentaquark with $\gamma $, $\pi ^{-}$ and K$^{+}$ beams Invited Speaker: Several experiments to search for the pentaquark, $\Theta ^{+}$, have been made with $\gamma $, $\pi ^{-}$ and K$^{+}$ beams at SPring8 and KEK-PS. It is important to observe the signal with both $\gamma $ and hadron beams at low energies for the confirmation of $\Theta ^{+}$. The KEK-E522 has searched for $\Theta ^{+}$ through $\pi ^{-}$+p -$>$ K$^{-}+\Theta ^{+}$ reaction. The KEK-E559 searches for $\Theta ^{+}$ through K+p -$>\pi ^{+}+\Theta ^{+}$ reaction with mass resolution of 1.3MeV(FWHM). Some results and status of thsese experiments are presented as well as those from SPring8. [Preview Abstract] |
Sunday, September 18, 2005 10:00AM - 10:30AM |
1WD.00003: Search for the $\Theta^+$ in high statistics photoproduction experiments with CLAS Invited Speaker: In the past two years more than 10 experiments have reported observation of a narrow exotic $S$=+1 baryon state in the mass range from $1.525$ to $1.55$ GeV/c$^2$. The minimal quark content of this state, called the $\Theta^+$, is $uudd\bar{s}$. There have been a number of reports of non-observation of this state, mostly in high energy inclusive experiments. The main criticisms of the reported $\Theta^+$ signals are insufficient statistics, and variation in mass. The CLAS Collaboration at Jefferson Laboratory has published two papers on the experimental evidence for the $\Theta^+$, based on the analysis of previously collected CLAS photoproduction data from hydrogen and deuterium. During the past year, the CLAS Collaboration has conducted two new dedicated high-statistics experiments to search for the $\Theta^+$. These data now represent the world's largest data sets for photoproduction on hydrogen and deuterium at energies up to 3.6 GeV. In this talk we present results in several reaction channels in a comprehensive search for the $\Theta^+$ from these experiments. [Preview Abstract] |
Sunday, September 18, 2005 10:30AM - 11:00AM |
1WD.00004: Nonstandard Mesons Invited Speaker: |
Sunday, September 18, 2005 11:00AM - 11:30AM |
1WD.00005: Search for Exotic Baryons at HERMES Invited Speaker: The prediction of narrow exotic baryon resonances based on the chiral soliton model has triggered an intensive search for the exotic members of an antidecuplet with spin 1/2. In this antidecuplet all three vertices are manifestly exotic. The lightest exotic member lying at its apex, named the $\Theta^+$, is predicted to have a mass near 1530 Mev and a narrow width. Its existence is currently the subject of considerable controversy. Experimental evidence for a second exotic member of the antidecuplet came from the reported observation of a $S$ =-2, $Q$=-2 baryon resonance in proton-proton collisions at $\sqrt{s}$=17.2 GeV. An experimental search for the $\Theta^{+}(1530)$ and $\Xi^{--}(1862) $ resonances has been performed by the HERMES collaboration using the decay modes $pK_s$ and $\Xi^- \pi^-$, respectively. While evidence for a peak at 1530 MeV with a statistical significance of $4\sigma$ is observed that can be interpreted as the $pK_s$ decay of the $\Theta^{+}$, no evidence for the $\Xi^{--}(1862)$ is found. The absence of a peak in the $\Xi^- \pi^-$ spectrum near 1862 MeV allows only an estimate of an upper limit for quasi-real photoproduction of the $\Xi^{--}(1862)$. Systematic studies and future plans will be discussed as well. [Preview Abstract] |
Sunday, September 18, 2005 11:30AM - 12:00PM |
1WD.00006: Recent Results on Pentaquark Searches from STAR Invited Speaker: We have examined the $p$+K$^+$ and $\overline{p}$+K$^-$ invariant mass distribution and observe a peak structure with approximately 4-5 sigma statistical significance in d+Au collisions at $\sqrt{s_ {NN}}$ 200 GeV and Au+Au collisions at 62.4 GeV. The apparent mass of the observed peak is at 1530 MeV/c$^2$. Its width is consistent with detector resolution. The nature of the peak is under active investigation. If confirmed as a particle, this state would be manifestly exotic with uuud-$\overline{s}$ quark structure. The observed yield is estimated to be very small. No signal above combinatoric background was observed in STAR p+p and Au+Au collisions at 200 GeV from RUN II. New analysis results from larger data samples of Run IV Au+Au 200 GeV and Run V Cu+Cu 62.4 GeV will be reported and the status of such pentaquark searches in general will be discussed. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700