2,160 research outputs found

    New Particles from Belle

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    I report recent results on hidden charm spectroscopy from Belle. These include: observation of a near-threshold enhancement in the omega-J/psi invariant mass distribution for exclusive B-->K omega J/psi decays; evidence for the decay X(3872)-->pi+pi-pi0 J/psi, where the pi+pi-pi0 invariant mass distribution has a strong peak between 750 MeV and the kinematic limit of 775 MeV, suggesting that the process is dominated by the sub-threshold decay X-->omega J/psi; and the observation of a peak near 3940 MeV in the J/psi recoil mass spectrum for the inclusive continuum process e+e- --> J/psi X. The results are based on a study of a 287 fb-1 sample of e+e- annihilation data collected at center- of-mass energies around the Upsilon(4S) in the Belle detector at the KEKB collider.Comment: 10 pages 12 figures. Invited talk at the 1st meeting of the APS Topical Group on Hadronic Physics, Fermilab, October 24-26, 2004; revised to correct some reference

    Search for X(3872) in gamma gamma Fusion and ISR at CLEO

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    We report on a search for the X(3872) state using 15.1 fb^{-1} of e+ e- annihilation data taken with the CLEO III detector in the sqrt{s} = 9.46-11.30 GeV region. Separate searches for the production of X(3872) in untagged gamma gamma fusion and e+ e- annihilation following initial state radiation are made by taking advantage of the unique correlation of J/psi -> l+ l- in X(3872) decay into J/psi pi+ pi-. No signals are observed in either case, and 90% confidence upper limits are established as (2J+1)Gamma_{gammagamma}(X(3872))B(X -> J/psi pi+ pi-) J/psi pi+ pi-) < 8.3 eV.Comment: 4 pages, 2 figures, to appear in the proceedings of the 1st Meeting of the APS Topical Group on Hadronic Physics, Fermilab, Oct. 24-26, 200

    How Resonances can synchronise with Thresholds

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    The mechanism by which a threshold may capture a resonance is examined. It involves a threshold cusp interfering constructively with either or both (i) a resonance produced via confinement, (ii) attractive t- and u-channel exchanges. The fo(980), X(3872) and Z(4430) are studied in detail. The fo(980) provides a valuable model of the locking mechanism. The X(3872) is too narrow to be fitted by a cusp, and requires either a resonance or virtual state. The Z(4430) can be fitted as a resonance but also can be fitted successfully by a cusp with no nearby resonant pole.Comment: 19 pages, 6 figures. Replaces 0709.125

    Simultaneous X-ray and Optical Observations of EX Hydrae

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    The intermediate polar, EX Hydrae, was the object of a large simultaneous multiwavelength observational campaign during 2000 May - June. Here we present the Rossi X-ray Timing Explorer photometry and optical photometry and spectroscopy from ground-based observatories obtained as part of this campaign. Balmer line radial velocities and Doppler maps provide evidence for an extended bulge along the outer edge of the accretion disk and some form of extended/overflowing material originating from the hot spot. In addition, the optical binary eclipse possesses an extended egress shoulder, an indication that an additional source (other than the white dwarf) is coming out of eclipse. We also compare the X-ray and optical results with the results obtained from the EUV and UV observations from the multiwavelength data set.Comment: to appear in the Astronomical Journal, April 200

    Precision lattice QCD calculations and predictions of fundamental physics in heavy quark systems

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    I describe the recent success in performing accurate calculations of the effects of the strong force on particles containing bottom and charm quarks. Since quarks are never seen in isolation, and so cannot be studied directly, numerical simulations are key to understanding the properties of these particles and extracting information about the quarks. The results have direct impact on the worldwide experimental programme that is aiming to determine the parameters of the Standard Model of particle physics precisely and thereby uncover or constrain the possibilities for physics beyond the Standard Model. The numerical simulation of the strong force is a huge computational task and the recent success is the result of international collaboration in developing techniques that are fast enough to do the calculations on powerful supercomputers.Comment: Invited talk at SCIDAC 2006, Denver, June 2006. 15 page

    EUVE Observations of the Magnetic Cataclysmic Variable QQ Vulpeculae

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    We present simultaneous X-ray (lambda_peak ~ 44A) and EUV (lambda_peak = 89A) light curves for the magnetic cataclysmic variable QQ Vulpeculae, obtained with the EUVE satellite. We find that the unique shape of the X-ray light curve is different from previously obtained X-ray light curves of QQ Vul and provides evidence for two-pole accretion. Detailed examination of the photometric data indicates that QQ Vul undergoes a stellar eclipse of the X-ray emitting region, indicative of a high binary inclination. We discuss possible implications for the nature of this system given the observed shape of its EUV and X-ray light curves.Comment: 12 pages including 4 figures, accepted to PAS

    Partial waves of baryon-antibaryon in three-body B meson decay

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    The conspicuous threshold enhancement has been observed in the baryon-antibaryon subchannels of many three-body B decay modes. By examining the partial waves of baryon-antibaryon, we first show for B- -->pp-bar K- that the pK- angular correlation rules out dominance of a single pp-bar partial wave for the enhancement, for instance, the resonance hypothesis or the strong final-state interaction in a single channel. The measured pK- angular correlation turns out to be opposite to the naive expectation of the short-distance picture. We study the origin of this reversed angular correlation in the context of the pp-bar partial waves and argue that NN-bar bound states may be the cause of this sign reversal. Dependence of the angular correlation on the pp-bar invariant mass is very important to probe the underlying problem from the experimental side.Comment: 16 pages, 9 figures, the version for journal publicatio

    An EUV Study of the Intermediate Polar EX Hydrae

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    On 2000 May 5, we began a large multi-wavelength campaign to study the intermediate polar, EX Hydrae. The simultaneous observations from six satellites and four telescopes were centered around a one million second observation with EUVE. Although EX Hydrae has been studied previously with EUVE, our higher signal-to-noise observations present new results and challenge the current IP models. Previously unseen dips in the light curve are reminiscent of the stream dips seen in polar light curves. Also of interest is the temporal extent of the bulge dip; approximately 0.5 in phase, implying that the bulge extends over half of the accretion disk. We propose that the magnetic field in EX Hydrae is strong enough (a few MG) to begin pulling material directly from the outer edge of the disk, thereby forming a large accretion curtain which would produce a very broad bulge dip. This would also result in magnetically controlled accretion streams originating from the outer edge of the disk. We also present a period analysis of the photometric data which shows numerous beat frequencies with strong power and also intermittent and wandering frequencies, an indication that physical conditions within EX Hya changed over the course of the observation. Iron spectral line ratios give a temperature of log T=6.5-6.9 K for all spin phases and a poorly constrained density of n_e=10^10-10^11 cm^-3 for the emitting plasma. This paper is the first in a series detailing our results from this multi-wavelength observational campaign.Comment: 27 pages, 7 figures, accepted for publication in Ap
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