Charmed particles production in pA-interactions at 70 GeV

The results of the SERP-E-184 experiment at the U-70 accelerator (IHEP, Protvino) are presented. Interactions of the 70 GeV proton beam with carbon, silicon and lead targets were studied to detect decays of charmed $D^0$, $\bar D^0$, $D^+$, $D^-$ mesons and $\Lambda_c^+$ baryon near their production threshold. Measurements of lifetimes and masses have shown a good agreement with PDG data. The inclusive cross sections of charm production and their A-dependencies have been obtained. The yields of these particles are compared with the theoretical predictions and the data of other experiments. The measured cross section of the total open charm production $\sigma(c\bar c) = 7.1 \pm 2.3(stat) \pm 1.4(syst)$ $\mu$b/nucleon at the collision c.m. energy $\surd s$ = 11.8 GeV is well above the QCD model predictions. The contributions of different kinds of charmed particles to the total cross section of the open charm production in proton-nucleus interactions vary with energy.Comment: Presented at 19th International Seminar on High Energy Physics QUARKS-2016 (Pushkin, Russia, 29 May - 4 June, 2016.). 11 pages, 9 figure

RAMPEX - a new spin experiment (presented for HELION97, 20-24 Jan 1997, Kobe, Japan)

RAMPEX - Russian-AMerican Polarization EXperiment - is dedicated to studies of one-spin asymmetries which have twist-3 and also twist-2 origin, in hard and semi-hard inclusive processes on the polarized propane-diol target. A special consideration has been given for the prospects of using polarized 3He target. The studies will be performed at the Serpukhov accelerator at 70 GeV/c (proton beam) and 40 GeV/c (pi- beam).Comment: 8 pages, 1 figur

Inclusive pentaquark and strange baryons production in pp and \Sigma p collisions at high energy

We calculate the cross sections for the inclusive production in the fragmentation region of $\Theta^+(1540)$ and $\Lambda(1520)$ in $pp$ collisions and $\Lambda(1520)$ in $\Sigma p$ collisions at high energy using the $K$- and $\pi$-meson exchange diagrams, respectively. The contributions of these diagrams survive at asymptotically large energies and are energy independent in this region up to logarithmic and power corrections. We find that inclusive $\Theta^+(1540)$ production should be at the level of 1 $\mu\mathrm{b}\times\Gamma_{\Theta KN}/ 1$ MeV. The ratio of the $\Theta^+(1540)$ over the $\Lambda(1520)$ yields is found to be $\sim 1$. The fraction of $\Lambda(1520)$ yields in $\Sigma p$ and $pp$ collisions is $\sim 2.7$ that quantitatively agrees with the preliminary result of the Fermilab fixed target experiment E781.Comment: 5 pages, 5 figures, 1 table; RevTeX

Absence of evidence for pentaquarks on the lattice

We study the question of whether or not QCD predicts a pentaquark state. We use the improved, fixed point lattice QCD action which has very little sensitivity to the lattice spacing and also allows us to reach light quark masses. The analysis was performed on a single volume of size $(1.8 {\rm fm})^3\times 3.6 {\rm fm}$ with lattice spacing of $a=0.102$ fm. We use the correlation matrix method to identify the ground and excited states in the isospin 0, negative parity channel. In the quenched approximation where dynamical quark effects are omitted, we do not find any evidence for a pentaquark resonance in QCD.Comment: 17 pages, 5 figures replaced with revised versio

Properties of the Lambda(1520) Resonance from High-Precision Electroproduction Data

High-resolution spectrometer measurements of the reaction H(e,e'K+)X at small Q2 are used to extract the mass and width of the Lambda(1520). We investigate the influence of various assumptions used in the extraction. The width appears to be more sensitive to the assumptions than the mass. To reach a width uncertainty about 1 MeV or better, one needs to know the structure of the non-resonant background. Based on the new Jefferson Lab Hall A data, our final values for the Breit-Wigner parameters are M = 1520.4 +- 0.6 (stat) +- 1.5 (syst) MeV, Gamma = 18.6 +- 1.9 (stat) +- 1 (syst) MeV. For the first time, we also estimate the pole position for this resonance and find that both the pole mass and width seem to be smaller than the Breit-Wigner values.Comment: 7 pages, 3 figures; corresponds to the published versio

Further study on 5q configuration states in the chiral SU(3) quark model

The structure of the $5q$ configuration states with strangeness ${\cal{S}}=+1$ is further studied in the chiral SU(3) quark model based on our previous work. We calculate the energies of fifteen low configurations of the $5q$ system, four lowest configurations of $J^{\pi}={1/2}^-$ with $4q$ partition $[4]_{orb}(0s^4)[31]^{\sigma f}$, four of $J^{\pi}={1/2}^+$ with $4q$ partition $[31]_{orb}(0s^30p)[4]^{\sigma f}$ and seven of $J^{\pi}={1/2}^+$ with $4q$ partition $[4]_{orb}(0s^30p)[31]^{\sigma f}$. Some modifications are made in this further study, i.e., the orbital wave function is extended as an expansion of 4 different size harmonic oscillator forms; three various forms (quadratic, linear and error function form) of the color confinement potential are considered; the states with $4q$ partition $[4]_{orb}(0s^30p)[31]^{\sigma f}$ are added, which are unnegligible in the $J^{\pi}={1/2}^+$ case and were not considered in our previous paper, further the mixing between configurations $[31]_{orb}(0s^30p)[4]^{\sigma f}$ and $[4]_{orb}(0s^30p)[31]^{\sigma f}$ is also investigated. The results show that the T=0 state is still always the lowest one for both $J^{\pi}={1/2}^-$ and $J^{\pi}={1/2}^+$ states, and $J^{\pi}={1/2}^-, T=0$ state is always lower than that of $J^{\pi}={1/2}^+$. All of these modifications can only offer several tens to hundred MeV effect, and the theoretical value of the lowest state is still about 245 MeV higher than the experimental mass of $\Theta^+$. It seems to be difficult to get the calculated mass close to the observed one with the reasonable parameters in the framework of the chiral SU(3) quark model when the model space is chosen as a $5q$ cluster.Comment: 16 page

Two-Hadron-Irreducible QCD Sum Rule for Pentaquark Baryon

We point out that naive pentaquark correlations function include two-hadron-reducible contributions, which are given by convolution of baryon and meson correlation functions and have nothing to do with pentaquark. We show that the two-hadron-reducible contributions are large in the operator product expansion of the correlation functions of three existing works on the pentaquark. Therefore, it is dangerous to draw a conclusion from the sum rules using naive pentaquark correlation functions with naive ansatz for the spectral function under the dispersion integral. Instead, we propose to use the two-hadron-irreducible correlation function, which is obtained by subtracting the two-hadron-reducible contribution from the naive correlation function. Taking one of the works as an example we demonstrate how drastically the results can change if we remove the two-hadron-reducible part from the naive correlation function. We obtain the result opposite to the original work for the parity of the pentaquark.Comment: 12 pages, 3 figure

Searching regions of interest on vector local homogeneous scenes

© 2014, Pleiades Publishing, Ltd. A generalized solution of the problem of searching a scene’s fragments, called the regions of interest, for the case when a set of spatial superposed images serves as the initial information about the scene, is proposed. A vector homogeneous random field is taken to be the scene model

The Experimental Search for Pentaquark

The existence of an anti-decuplet of pentaquark particles has been predicted some year ago within the chiral soliton model. In the last year, several experimental groups have reported evidence for a S=+1 baryon resonance, with mass ranging from 1.52 and 1.55 GeV and width less than 25 MeV, by looking at the invariant mass of the $K N$ system. This resonance, has been identified with the lowest mass of the anti-decuplet, the $\Theta^+$. At the same time, there are a number of experiment, mostly at high energies, that report null results. An overview of the experimental results so far obtained will be given here together with a review of the second generation experiments currently ongoing and planned at Jefferson Lab Hall B.Comment: 10 pages, 9 figures, 3 tables Proceedings of the INCP2004 Conference - Goteborg (Sweden) June 27 - July 2, 200

Photoproduction of the Theta^+ and its vector and axial-vector structure

We present recent investigations on the vector and axial-vector transitions of the baryon antidecuplet within the framework of the self-consistent SU(3) chiral quark-soliton model, taking into account the 1/N_c rotational and linear m_s corrections. The main contribution to the electric-like transition form factor comes from the wave-function corrections. This is a consequence of the generalized Ademollo-Gatto theorem. It is also found that in general the leading-order contributions are almost canceled by the rotational 1/N_c corrections. The results are summarized as follows: the vector and tensor K^*-N-Theta coupling constants, g_{K^*-N-Theta}=0.74 - 0.87 and f_{K^*-N-Theta}=0.53 - 1.16, respectively, and Gamma_{Theta->KN}=0.71 MeV, based on the result of the K-N-Theta coupling constant g_{K-n-Theta}=0.83. We also show the differential cross sections and beam asymmetries, based on the present results. We also discuss the connection of present results with the original work by Diakonov, Petrov, and Polyakov.Comment: 9 pages, 6 figures, An invited talk given at the Workshop of Excited Nucleon - NSTAR2009 held in Beijing, April 19-22 200