Exotic narrow resonance searches in the systems K s 0 p, K s 0 and p in pA-interactions at 10 GeV/c Petros Aslanyan 1,2,† (1) Joint Institute for Nuclear Research. (2) Yerevan State University. † 1. Introduction. 2. Method. 3.Invariant mass spectrum analysis : 3.1. (K s 0 p)- system 3.2. ( K s 0 ) -system 3.3 ( p ) - system. Conclusion. The XVIIth International Conference on Elastic and Diffractive Scattering the Château Royal de Blois, France, from Sunday, May 15-20, 2005.
c.f. (1405): uudsu or uds e.g. uuddc, uussd What are penta-quarks? 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 = = 1
[1] D. Diakonov, V. Petrov, and M. Polyakov, Z. Phys. A 359 (1997) 305. [2] V.Guzey and M.Polyakov, arXiv hep- ph/ ,2005. Exotic: S= +1Exotic: S= +1 Results from a wide range of recent experiments are consistent with the existence of an exotic S=+1 resonance, the +(1540) with a narrow width and a mass near 1540 MeV [1]. Narrow width: < 15 MeV Results from this experiment: M = (1540 8) M + = (1540 8) MeV/c 2, 1.8) + =(9.2 1.8) MeV/c 2. PDG-04: 0.3) + =(9.2 0.3) MeV/c 2. Multi-quark states, glueballs and hybrids have been searched for experimentally for a very long time, but none is established. Meson （ q q ） Baryon （ q q q ）
Evidence for Penta-Quark States Spring8 ELSA JLab-p HERMES ITEP pp + +. COSY-TOF DIANA SVD/IHEP JLab-d ZEUS CERN/NA49 H1 Nomad This is a lot of evidence. However,…
Ξ -- (1862) Also evidence for Ξ 0 (1862) ( I = 3/2 ) ( I = 3/2 ) NA49 pp collision at E cm =17.2GeV
Studies 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) [Polyakov M.]. Jafe and Wilczek predicted a mass around 1750MeV and a width 50% larger for these states than that of the Θ+. S.Kabana observes a narrow peak at 1734 ± 0.5 ± 5 MeV (,hep-ex/ ) width consistent with the experimental resolution of about 6 MeV within the errors and only a weak indication of a narrow peak at 1693 ± 0.5 MeV in the K S 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 N 0 or the * I=1/2 pentaquark states. Exotic: S= 0Exotic: S= 0 Low mass: 1710 MeV Narrow width: < 40 MeV Jp=1/2+
p p The problem of experimental examination of multibaryon strange resonances was started at JINR, LHE from 1962 up to now. The effective mass spectra of 17 strange multiquark systems were studied for neutron exposure nC X at average momentum 7.0 GeV/c, and this group succeeded in finding resonance-like peaks [1-3] only in five of them p, p , , p, . Most significant evidence was included in the Review of Particle Properties. Preliminary results[4] in pC collision at 10 GeV/c show that the obtained peaks in reports [1-3] has been confirmed. 1) B.A. Shahbazian et al., Nucl. Physics, A374(1982),p. 73c-93.c.2) B.A. Shahbazian,JINR Commun., E ,1982, International Conference on Hypernuclear and Kaon Physics, Heidelberg, ) B.A. Shakhbazian et al., (Dubna, JINR). JINR-D , P.Z. Aslanyan, hep- ex/ ,2003.
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 stereo photographs are used to select the events with V 0 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%, =12 cm for stopping particles and P/P =9.8 %, = 36 cm for non stopping particles. The mean values of measurement errors for the depth and azimuthal angles are equal to tg = ± and = ± (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: P GeV/c. 2. Experiment
The events with V 0 ( and K s 0 ) were identified by using the following criteria [20-22]: 1) V 0 stars from the photographs were selected according to - +p, K s 0 - + or e + +e - hypothesis. A momentum limit of K s 0 and is greater than 0.1 and 0.2 GeV/c, respectively ; 2) V 0 stars should have the effective mass of or of K s 0 ; 3) these V 0 stars are directed to some vertices(complanarity); 4) they should have one vertex, a three constraint fit for the M K or M hypothesis and after the fit, 2 should be selected over range less than 12; 5) The analysis has shown[21] that the events with undivided K s 0 were assumed to be . [21] E.N.Kladnitskaya, K.J.Jovchev, P JINR,1986. Distributions of (Armenteros parameter) and cos * - are used for correctly identification of the undivided V 0 s. = (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 K s 0 decay. Distributions of and cos * - were isotropic in the rest frame of K s 0 when undivided K s 0 were assumed to be . Identification and K 0 s The events with V 0 ( and K s 0 ) were identified by using the following criteria [20-22]: 1) V 0 stars from the photographs were selected according to - +p, K s 0 - + or e + +e - hypothesis. A momentum limit of K s 0 and is greater than 0.1 and 0.2 GeV/c, respectively ; 2) V 0 stars should have the effective mass of or of K s 0 ; 3) these V 0 stars are directed to some vertices(complanarity); 4) they should have one vertex, a three constraint fit for the M K or M hypothesis and after the fit, 2 should be selected over range less than 12; 5) The analysis has shown[21] that the events with undivided K s 0 were assumed to be . [21] E.N.Kladnitskaya, K.J.Jovchev, P JINR,1986. Identification and K 0 s
Figures (a,c) and (b,d) show the effective mass distribution of 8657-events with , 4122-events with K s 0 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 M K = 497.7± 3.6, s.d.= 23.9 MeV/c 2 and M = ± 0.6, s.d.=10.0 MeV/c 2. The masses of the observed , K s 0 are consistent with their PDG values. The preliminary estimate of the experimental total cross sections is equal to 3.8 ± 0.6 mb for K s 0 production in the p+C collisions at 10 GeV/c.
Each V 0 event weighted by a factor w geom (=1/e ), where e is the probability for potentially observing the V 0, it can be expressed as:e = e (-Lmin/L) - e (-Lmax/L), where L(=cp /M) is the flight length of the V 0, L max the path length from the reaction point to the boundary of fiducial volume, and L min (0.5 cm) an observable minimum distance between the reaction point and the V 0 vertex. M, , and p are the mass, lifetime, and momentum of the V 0. The average geometrical weights were 1.34 0.02 for and 1.22 0.03 for K 0 s. The effective mass resolution of the K s 0 and Ks0p systems, like that of the - +p system, has been measured with a precision of M Ks /M Ks =(1.0 0.1)%(Fig.). Then the effective mass resolution of + K s 0 p system was estimated to be on the average 0.6 % for identified protons with a momentum of P GeV/c. The estimation of experimental inclusive cross sections for and K s 0 production in the p+C collision is equal to =1 3.3 1.7 mb and Ks0 = 3.8 0.6 mb, respectively \cite{23}.
Figure compares the momentum, cos in the c.m. nucleon-nucleon system, transverse momentum(p t ) and longitudinal rapidity distributions of and K 0 s 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.
3.Invariant mass 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 30 %. This distribution was fitted by the six-order polynomial. The second of the randomly mixing method of the angle between K 0 s and p for experimental events is described in V.L.Lyuboshits at al., JINR Rapid Comm., N6(74),p209, Then, these background events were analyzed by using the same experimental condition and the effective mass distribution ( K 0 s p ) was fitted by the six-order polynomial. The analysis done by two methods has shown that while fitting these distributions had the same coefficients( with 20 % 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}.
3.1.K s 0 p - spectrum analysis The Ks0p effective mass distribution for identified protons with a momentum of P GeV/c is shown in Figure. The solid curve is the sum of the background and 4 Breit-Wigner resonance curves The Ks0p invariant mass distribution with a momentum Pp 1.7 GeV/c (3500 combinations) is shown in Figure. The histogram is approximated by a polynomial background curve and by 5 resonance curves taken in the Breit-Wigner form. The dashed curve is the background taken in the form of a superposition of Legendre polynomials up to the 6 -th degree, inclusive.
The Ks0 effective mass distribution for 1012 combinations is shown in Figure. The solid curve is the sum of the background by the first method and Breit-Wigner resonances. Similar results have obtained when using a Breit Wigner distribution and diferent bin sizes. There are significant enhancements in mass regions of 1750 and 1795 MeV/c 2 (Fig.). There are small peaks in the mass regions of ( ),( ) and ( ) MeV/c K s 0 - spectrum analysis
3.3. p - spectrum analysis The p effective mass distribution for 2434 combinations for identified protons with a momentum of P GeV/c is shown in Figure. The solid curve is the sum of the background by the first method and Breit-Wigner resonances. There are significant enhancements in mass regions of 2101, and 2353 MeV/c 2 (Fig.). Their excess above background by the second method is 6.9, 4.9, 3.8 and 2.9 S.D., respectively.
Conclusion The effective mass spectra K s 0 p in collisions protons of a 10 GeV/c momentum with propan nuclei, have resulted in the discovery of the peaks presented below(Table 1). Table 1 shows the width( ) and the effective mass resonances which are based on the data from figure with a momentum range of P proton GeV/c. There are small peaks in mass regions of 1487(3.0 s.d.), 1690(3.6 s.d.) and 1980(3.0 s.d.) MeV/c 2. The primary total cross section for + (1540) production in p+C 3 H 8 interactions is estimated to be 90 b. Table 1. The effective mass spectra K s 0 p have resulted in the discovery of the peaks presented below
A number of peculiarities were found in the effective mass spectrum of system K s 0 in ranges of:( ), ( ) and ( ) МэВ/с 2 in collisions of protons of a 10 GeV/c momentum with propane nuclei(Table 2). There are small enhancements in the mass spectrum regions of ( ) and ( ) МэВ/с 2. The prelimary total cross section for N 0 (1750) production in p+C 3 H 8 interactions is estimated to be 30 b. The N 0 can be from the antidecuplet, from an octet (D. Diakonov, V. Petrov, hep-ph/ , V.Guzey and M.Polyakov, arXiv hep-ph/ ,2005) or an 27- plet(J. Ellis et al, JHEP 0405:002, 2004, hep-ph/ ). On the other hand, Jafe 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) ). Resonance decay mode M M (MeV/c 2 ) Experimental Width e The maximal statistical significance 0 s 1750 6 14 0 s 1795 0 s 1850 7 10 Table 2. 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.
These peaks are possible candidates for two pentaquark states: the N 0 with quark content udsds decaying into K 0 and the 0 quark content udssd decaying into ( K 0 )(Table 3), which are agreed: with the calculated rotational spectra N 0 and 0 spectra from the theoretical report of D. Akers, arXiv.org:hep-ex/ , 2004 (below figure) and with + spectra from the experimental reports of Yu.A.Troyan et.al.,JINR, D , Dubna,2004 and P. Aslanyan JINR, E ,2004 (Table 2).
Type of resonance Resonance decay mode The effective Mass(MeV/c 2 ) (*- >100MeV) Reference **N*N*N*N*N*N*N*N*++++**N*N*N*N*N*N*N*N*++++ K0sK0sK0sK0sNNK0sK0sK0sK0sK0spK0spK+nK+nK0sK0sK0sK0sNNK0sK0sK0sK0sK0spK0spK+nK+n * PDGPDG GRAAL collab., hep-ex/ ,2004 This experiment S.Kabana hep-ex/ ,2004 P.Aslanyan et al., JINR,E ,2004 Yu.A.Troyan et al., JINR, D , 2004 N*N*N*N* N* N***N*N*N*N* N* N*** NNK0sK0sK0sK0s--NNK0sK0sK0sK0s- 9* 1734 KH collab., KH collab., Koch R 1985 Z. Phys. C 29, 597 S.Kabana hep-ex/ ,2004 This experiment ZEUS Collaboration, hep-ex/ , 2005 **N*N*++++++**N*N*++++++ K0sK0sK0sK0sK+nK+nK0spK0spK0spK0spK0sK0sK0sK0sK+nK+nK0spK0spK0spK0sp 11 PDG(1976,2004) PDG(1976,2004) This experiment Yu.A.Troyan et al., JINR, D , 2004 P.Aslanyan et al., JINR, E ,2004 --, -, 0 N * + K0sK0sK+nK+nK0sK0sK+nK+n Alt C et al. Phys. Rev. Lett , 2004 This experiment Yu.A.Troyan et al., JINR, D , 2004 Table 3. The mass of N 0, 0, * and + baryon resonances in range of MeV/c 2 are presented.
Preliminary experimental results for S=-1 p dibaryon resonancesin pC p X collision at 10 GeV/c (Table 4) shows that the predicted peaks with the bag model has been confirmed (P.Z. Aslanyan, hep-ex/ ,2003). Preliminary experimental results for S=-1 p dibaryon resonances in pC p X collision at 10 GeV/c (Table 4) shows that the predicted peaks with the bag model has been confirmed (P.Z. Aslanyan, hep-ex/ ,2003). Table 4. The p effective mass spectra in collisions of protons at 10 GeV/c andneutrons of at 7.0 GeV/c average momentumwith carbon nuclei. protons at 10 GeV/c and neutrons of at 7.0 GeV/c average momentum with carbon nuclei (B.A. Shahbazian et al., Nucl. Physics, A374(1982),p. 73c-93.c.2).