Means for Testing and Adjusting the Magnetic Spectrometer of the SVD-2 Facility

Aleev, A.N.; Basiladze, S.G.; Vishnevskaya, A.M.

doi:10.1023/b:inet.0000049695.75056.fe

Cited by 11 publications

(17 citation statements)

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“…Manifestations of the Θ + -production mechanism are possibly seen also in preliminary data of the SVD Collaboration. Its higher-statistics analysis [25,26] has confirmed the earlier evidence for production of the Θ + (1530) in nucleon-nucleon collisions [63]. Moreover, preliminary data of this collaboration provide distributions of the Θ + in the Feynman variable x F and in p T .…”

Section: Positive Datasupporting

confidence: 74%

“…But we expect that the relative yield of the exotic Θ + -baryon vs. a conventional baryon, say, Λ(1520) , should be enhanced for such events in comparison to the total set of events. Properties of the Θ + -production, as observed by the SVD Collaboration [25,26,63,64], show that also useful for the exotics observation might be restriction to relatively low energy of the (KN)-pair (as we have explained, this is also related to the enlarged multiplicity).…”

Section: Suggestions For Further Experimentsmentioning

confidence: 85%

“…Especially impressive are the recent high-statistics null results of the CLAS Collaboration for Θ + -photoproduction in several final-states [20,21,22,23]. And yet, new ("after-CLAS") dedicated analyses have again provided both confirming [24,25,26,27,28] and null [29,30,31,32,33] publications. Moreover, a new suggested way [34] for data analysis may reveal presence of the Θ + even in the published CLAS results, through its interference with a known resonance.…”

Section: Introductionmentioning

confidence: 99%

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Explanation why theΘ+is seen in some experiments and not in others

2007

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To understand the whole set of positive and null data on the Θ + (1530)-production, we suggest the hypothesis that multiquark hadrons are mainly generated from many-quark states, which emerge either as short-term hadron fluctuations, or as hadron remnants in hard processes. This approach allows us to describe both non-observation of the Θ + in current null experiments and peculiar features of its production in positive experiments. Further, we are able to propose new experiments that might be decisive for the problem of the Θ + existence. Distributions of the Θ + in such experiments can give important information both on higher Fock components of conventional hadrons and about structure and hadronization properties of hadron remnants produced in hard processes. We also explain that description of multiquark hadrons may require a modified form of the constituent quark model, with quark masses and couplings being intermediate between their values for the familiar constituent quarks and the current ones.

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Section: Positive Datasupporting

confidence: 74%

Section: Suggestions For Further Experimentsmentioning

confidence: 85%

Section: Introductionmentioning

confidence: 99%

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Explanation why theΘ+is seen in some experiments and not in others

2007

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“…On the other hand, the DIANA collaboration has continued to search for the Θ + and reported very recently the formation of a narrow pK 0 peak with mass of 1537±2 MeV/c 2 and width of Γ = 0.36 ± 0.11 MeV in the K + n → K 0 p reaction [26]. Moreover, several other new experiments with positive results for the Θ + have been reported [27,28,29,30,31]. Thus, it is too early to conclude the absence of the Θ + and more efforts should be put for understanding the Θ + theoretically as well as experimentally.…”

Section: Introductionmentioning

confidence: 99%

Vector transition form factors of the and in the chiral quark–soliton model

Ledwig¹,

Kim²,

Goeke³

2008

Nuclear Physics A

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We investigate the vector transition form factors of the nucleon and vector meson K * to the pentaquark baryon Θ + within the framework of the SU(3) chiral quark-soliton model. We take into account the rotational 1/N c and linear m s corrections, assuming isospin symmetry and employing the symmetry-conserving quantization. It turns out that the leading-order contributions to the form factors are almost cancelled by the rotational corrections. Because of this, the flavor SU(3) symmetry-breaking terms yield sizeable effects on the vector transition form factors. In particular, the main contribution to the electric-like transition form factor comes from the wave-function corrections, which is a consequence of the generalized Ademollo-Gatto theorem derived in the present work. We estimate with the help of the vector meson dominance the K * vector and tensor coupling constants for the Θ + : g K * N Θ = 0.74 − 0.87 and f K * N Θ = 0.53 − 1.16. We argue that the outcome of the present work is consistent with the null results of the CLAS experiments in the reactions γn → K − Θ + and γp →K 0 Θ + . The results of the present work are also consistent with the recent experiments at KEK. In addition, we present the results of the Σ 10 → NK * transition form factors and itsK * N Σ 10 coupling constants.

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“…The JINR result comes from an analysis of collisions in a propane bubble chamber exposed to a 10 GeV/c proton beam. The SVD experiment [11] at IHEP studied pA collisions at 70 GeV/c. Both the DIANA and νBC groups re-analyzed old data from a liquid xenon bubble chamber (in the case of DIANA) [12] and the CERN BEBC and the FNAL 15-foot chamber (in the case of νBC) [13] -the former using a low-energy K + beam, the the latter neutrinos.…”

Section: Experiments Claiming Positive Pentaquark Signalsmentioning

confidence: 99%

Reviewing the evidence for pentaquarks

Dzierba¹,

Meyer²,

Szczepaniak³

2005

J. Phys.: Conf. Ser.

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Abstract. Several experimental groups have reported evidence for baryons with flavor exotic quantum numbers that cannot be explained as qqq bound states but require a minimum of five quarks -qqqqq. These pentaquark states include the θ + , the Ξ −− and the θc. The reported widths of these new states are consistent with experimental resolution and may be as narrow as a few MeV/c 2 or less. Prior to 2003, experimental searches for flavor exotic baryons spanning several decades yielded negative results. There have also been a number of searches carried out since the reports of these new pentaquark states that do not confirm their existence. This review of both the positive and negative reports seeks to understand the current situation regarding the experimental evidence for pentaquarks. IntroductionIt is noteworthy that except for one or two possible exceptions in the meson sector, the hundreds of known hadrons can be described as bound states of three quarks (qqq), in the case of baryons, or a quark and anti-quark (qq), in the case of mesons. There have been reports of possible evidence of mesons with exotic J P C quantum numbers, not possible for qq, but until 2003, no reports of baryons with quantum numbers inconsistent with qqq. There were searches in the 1960's and 1970's for what was then referred to as the Z * -a baryon with positive strangeness. The review by Hey and Kelly [1] discusses these early searches, mostly in bubble chamber experiments, and a more recent review by Trilling of the current exotic baryon sightings [2] lists publications reporting on bubble chamber experiments with incident π and K beams searching for the Z * . Those experiments found no enhancements in S = +1 baryon channels. Indeed the failure to find such flavor exotic baryons in the 1960's and 1970's lent credence to the then nascent quark model.

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Means for Testing and Adjusting the Magnetic Spectrometer of the SVD-2 Facility

Cited by 11 publications

References 0 publications

Explanation why theΘ+is seen in some experiments and not in others

Explanation why theΘ+is seen in some experiments and not in others

Vector transition form factors of the and in the chiral quark–soliton model

Reviewing the evidence for pentaquarks

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