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Workshop on Hadron Structure at J-PARC

This workshop held at J-PARC in Tsukuba, Japan focused on the study of hadron structure through exotic narrow resonance searches in the Ks0Λ system. The workshop included presentations on quantum numbers, penta-quarks, and experimental results.

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Workshop on Hadron Structure at J-PARC

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  1. Workshop on Hadron Structure at J-PARC November 30 – December 2, 2005, Tsukuba, Ibaraki, Japan. High Energy Accelerator Research Organization (KEK) Exotic narrow resonance searches in the Ks0system in p+propane interactions at 10 GeV/cPetros Aslanyan 1,2,†(1) Joint Institute for Nuclear Research.(2) Yerevan State University . † paslanian@jinr.ru. Introduction. Method. ( Ks0 ) - spectrum analysis. Conclusion.

  2. What are penta-quarks? Meson（ qq ） Baryon（q q q） Minimum quark content is 5 quarks. “Exotic” penta-quarks are those where the antiquark has a different flavor than the other 4 quarks Quantum numbers cannot be defined by 3 quarks alone. Example: uudds Baryon number = 1/3 + 1/3 + 1/3 + 1/3 – 1/3 = 1 Strangeness = 0 + 0 + 0 + 0 + 1 = 1 e.g. uuddc, uussd c.f. L(1405): uudsu or uds

  3. Multi-quark states, glueballs and hybrids have been searched for experimentally for a very long time, but none is established. [1]D. Diakonov, V. Petrov, and M. Polyakov (Z. Phys. A 359 ,305 ,1997) and [2]V.Guzey and M.Polyakov(arXiv hep-ph/0501010,2005) predicted and studied antidecuplet baryons by using the chiral soliton (Skyrme) models. The lightest member of the pentaquarks antidecuplet has positive strangeness, the mass of M=1530 MeV/c2. • Exotic: S= +1 • Results from a wide range of experiments are consistent with the existence of an exotic S=+1 resonance, the +(1540) with a narrow width and a mass near1540 MeV . • Results from this experiment: • M + = (15408) MeV/c2, •  +=(9.21.8) MeV/c2. • PDG-04: •  +=(9.20.3)MeV/c2.

  4. JLab-d Spring8 DIANA ELSA ITEP SVD/IHEP JLab-p HERMES ZEUS COSY-TOF CERN/NA49 H1 pp  S+Q+. Evidence for Penta-Quark States this experiment Nomad

  5. Negative Results

  6. Ξ--(1862) NA49 pp collision at Ecm=17.2GeV • Also evidence for Ξ0(1862) ( I = 3/2 )

  7. Exotic: S= 0 • Low mass: 1710 MeV • Narrow width: < 40 MeV • Jp=1/2+[1] S.Kabanafrom STAR collaboration observed a narrow peak at 1734 ± 0.5 ± 5 MeV (hep-ex/0406032 ) width consistent with the experimental resolution of about 6 MeV within the errors and only aweak indication of a narrow peak at 1693 ± 0.5 MeV in the KS invariant mass. The statistical significance can be quantified between 3 and 6 depending on cuts and methods. If this peak corresponds to a real particle state it would be a candidate for the N0 or the * I=1/2 pentaquark states. Studies (Polyakov M.) which have claimed to see this state have given widely varying estimates of its mass and width (from 1680 MeV to 1740 MeV for the mass). Jaffe and Wilczek predicted a mass around 1750MeV and a width 50% larger for these states than that of the Θ+.

  8. 2. Experiment A reliable identification of the above mentioned resonance needs to use 4-detectors and high precision measurements of the sought objects. The bubble chamber is the most suitable instrument for this purpose . The experimental information of more than 700000 stereo photographs are used to select the events with V0 strange particles at collisions protons of a 10 GeV/c momentum with propan nuclei . The GEOFIT based on the Grind-CERN program is used to measure the kinematics parameter of tracks momenta(P), tg( - depth angle) and azimuthal angle() in the photographs. The relative error of measuring momentum p and the average track length L of charged particles are found to be P/P=2.1%, < L>=12 cm for stopping particles and P/P =9.8 %, <L>= 36 cm for non stopping particles. The mean values of measurement errors for the depth and azimuthal angles are equal to tg = 0.0099± 0.0002 and  = 0.0052± 0.0001 (rad.). The estimation of ionization, the peculiarities of the end track points of the stopping particles(protons, K ) allowed one to identify them. Protons can be identified over the following momentum range: 0.150 P  0.900 GeV/c.

  9. Identification  and K0s Identification  and K0s The events with V0( and Ks0) were identified by using the following criteria : 1) V0 stars from the photographs were selected according to -+p,Ks0-+ or e++e-hypothesis. A momentum limit of Ks0 and  is greater than 0.1 and 0.2 GeV/c, respectively ; 2) V0 stars should have the effective mass of or of Ks0; 3) these V0 stars are directed to some vertices(complanarity); 4) they should have one vertex, a three constraint fit for the MK or M hypothesis and after the fit,2should be selected over range less than 12; 5) The analysis has shown[21] that the events with undivided Ks0were assumed to be (Fig.) . [21] E.N.Kladnitskaya , K.J.Jovchev , P1-86-166 JINR,1986. Distributions of  (Armenteros parameter) and cos*- are used for correctly identification of the undivided V0s. = (P+ - P -)/(P+ + P- ). Where P+  and P-  are the parallel components of momenta positive and negative charged tracks. cos * - is the angular distribution of - from V0 decay in rest frame V0. Distributions of  and cos * - were isotropic in the rest frame of Ks0 when undivided  Ks0 were assumed to be  .

  10. Figures (a,c) and (b,d) show the effective mass distribution of 8657-events with , 4122-events with Ks0 particles and their 2 from kinematic fits, respectively. The expected functional form for 2 is depicted with the dotted histogram. The measured masses of these events have the following Gaussian distribution parameters MK= 497.7± 3.6, s.d.= 23.9 MeV/c2 and M  =1117.0 ± 0.6, s.d.=10.0 MeV/c2. The masses of the observed , Ks0 are consistent with their PDG values. The preliminary estimate of the experimental total cross sections is equal to 3.8 ± 0.6 mb for Ks0 production in the p+C collisions at 10 GeV/c.

  11. Each V0 event weighted by a factor wgeom (=1/e), where e is the probability for potentially observing the V0, it can be expressed as:e = e(-Lmin/L)- e(-Lmax/L) , where L(=cp/M) is the flight length of the V0 , Lmax the path length from the reaction point to the boundary of fiducial volume, and Lmin(0.5 cm) an observable minimum distance between the reaction point and the V0 vertex. M,, and p are the mass, lifetime, and momentum of the V0. The average geometrical weights were 1.34 0.02 for  and 1.22 0.03 for K0s. The effective mass resolution of the Ks0 system, like that of the   -+p system, has been measured with a precision of (M Ks ) /MKs  =(1.00.1)%(Fig.). The estimation of experimental inclusive cross sections for  and Ks0 production in the p+C collision is equal to  =13.3 1.7 mb and Ks0 = 3.8  0.6 mb, respectively .

  12. Figure compares the momentum, cos in the c.m. nucleon-nucleon system, transverse momentum(pt) and longitudinal rapidity distributions of  and K0s for experimental events (solid line) and those simulated by the FRITIOF model (broken line)in p+C interactions. From Fig. one can see that the experiment is satisfactorily described by the FRITIOF model.

  13. ( K s0 ) - spectrum analysis. The total experimental background has been obtained by three methods. In the first method, the experimental effective mass distribution was approximated by the polynomial function after cutting out the resonance ranges because this procedure has to provide the fit with 2=1 and polynomial coefficient with errors less than 10 %. The second of the randomly mixing method of the angle between K0s and  for experimental events is described in V.L.Lyuboshits at al., JINR Rapid Comm., N6(74),p209, 1995. Then, these background events were analyzed by using the same experimental condition and the effective mass distribution was fitted by the polynomial function. The analysis done by two methods has shown that while fitting these distributions had the same coefficients( with 10 % errors) and order of polynomial. The third background method has been obtained by using FRITIOF model with experimental canditions (FRITIOF, H. Pi, Comput. Phys.Commun. 71,173, 1992). Hereinafter, the Ks0 effective mass distribution for 1012 combinations is shown on Figure (next slide). The solid curve is the sum of the background by the first method and 2 Breit-Wigner resonance in Figure. The values for the mean position of the peak andthe width obtained by using Breit Wigner fits . The statistical significance for the fit on Fig. inside a mass window is calculated as NP /(NB)1/2, where NB is the number of counts in the background fit under the peak and NP is the number of counts in the peak.

  14. a There are significant enhancements in mass regions of 1750 and 1795 MeV/c2 (Fig.). Their excess above background by the first method is 5.8 and 3.3 S.D., respectively. There are small enhancements in the mass regions of (1650- 1700),(1830-1860) and (1925 -1950) MeV/c2 . This bin size of 18 MeV/c2 is agreed with the experimental resolution.

  15. This analysis of background by FRITIOF shows too that the simulated events could not imitate peaks with mass of 1750 and 1795 MeV/c2. Hereinafter, analysesof effective mass distributions have obtained similarly when using a Breit Wigner distribution and different binsizes.

  16. There are significant enhancements in mass regions of (1750 17), (179521) and (1835 20)MeV/c2 with bin size 10 MeV/c2 (Fig.). Their excess above background by the first method is 4.0, 2.7 , 3.0 S.D.. There is small enhancement in mass region of 1935 MeV/c2.

  17. We show a lot of statistical deviations except only over the range of 1750 MeV/c2 on Figure because there are not a enough statistics in bins of 6.5 MeV/c2 size. There is the significant peak in the mass region of (1750 16) MeV/c2. Their excess above background by the first method is 4.5 S.D..

  18. There is the significant peak in the mass region of (1742 14) MeV/c2 with bin size 21 MeV/c2 (Fig.). Their excess above background by the first method is equal to 5.0 S.D.. Figure shows insignificant deviations in mass regions of 1670, 1795, 1855 and 1935 MeV/c2 because this bin size is done larger than experimental resolution.

  19. The figure shows the invariant mass distributions of ( K0s) with bin size 11 MeV/c2 . There are enhancements in the mass regions 1670, 1750, 1795 and 1850MeV/c2. Their excess above background by the first method is 2.9, 4.7 , 2.3 and 2.4 S.D..

  20. Conclusion • A number of peculiarities were found in the effective mass spectrum of system Ks0in ranges of:((1650-1675 ),(1740-1750), (1785-1800), (1835-1860) and (1925-1950) МэВ/с2 in collisions of protons with propane nuclei at momentum 10 GeV/c.There are significant enhancements in the mass spectrum with bin size 18 МэВ/с2 only in regions of 1750 and 1795 МэВ/с2 (Table 1). • The prelimary total cross section for N0(1750) production in p+C3H8 interactions is estimated to be  30b. • The N0 can be from the antidecuplet, from an octet (D. Diakonov, V. Petrov, hep-ph/0310212, V.Guzey and M.Polyakov, arXiv hep-ph/0501010,2005) or an 27-plet(J. Ellis et al, JHEP 0405:002, 2004, hep-ph/0401127).On the other hand, Jaffe and Wilczek predicted a mass around 1750MeV and a width 50% larger for these states than that of the Θ+(Phys. Rev. Lett. 91 (2003) 232003). Table 1. The maximal statistical significance, the full experimental width(e) and the effective mass of resonances in collisions of protons with propane at 10 GeV/c.

  21. These peaks are possible candidates for two pentaquark states: the N0 with quark content udsds decaying into K0 and the 0 quark content udssd decaying into ( K0 ), which are agreed: with the calculated rotational spectra N0 and0 spectra for antidecuplet from theoretical report of D. Akers, arXiv.org:hep-ex/0310014, 2004 (below Table);)and with + spectra from the experimental reports of Yu.A.Troyan et.al.,JINR, D1-2004-39, Dubna,2004 and P. Aslanyan JINR, E1-2004-137,2004 (next slide ).

  22. Preliminary proposal The study of the structure of elementary particles and atomic nucleus at J-PARK. • Exoticmulti-quark hadronswith B=0,1,2,3and S=+1,0,-1,-2strangeness will be to search in systems from Ks0and particles for protron-nucleus interactions at beam momenta of 4-50 GeV/c. A statistical significance of identified resonances would be to improve. As a test would be to use the experimental data fron 2 m propane bubble chamber. • Experimental regularities for Ks0 , , and  strange particles productions and theirs exotic decays will study in protron-nucleus interactions at beam momenta of 4-50 GeV/c. For instance will be to study ratios of multiplicities for these strange particles on the + multiplicity in central ranges as a probe for searching QGP.

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