• Introduction• Method• (Ks

0p) - spectrum analysis• Conclusion

Evidence of S=+1 narrow resonances in the system (Ks

0p) Petros Aslanyan 1,2,3 et.al. (1) Joint Institute for Nuclear Research.

(2) Yerevan State University. (3) paslanian@jinr.ru.

October 11-16, 2004 @ Trieste, Italy

Parallel session 4 - Spin in Soft Hadronic Reactions

1. Introduction1. Introduction

Recent experimental efforts have been Recent experimental efforts have been strongly motivated by Diakonov, Petrov strongly motivated by Diakonov, Petrov and Polyakov [1] who studied antidecuplet and Polyakov [1] who studied antidecuplet baryons by using the chiral soliton baryons by using the chiral soliton (Skyrme) models. The lightest member of (Skyrme) models. The lightest member of the pentaquarks antidecuplet, the pentaquarks antidecuplet, (1530) -(1530) -baryon predicted in , has positive baryon predicted in , has positive strangeness, the mass of M=1530 MeV/cstrangeness, the mass of M=1530 MeV/c22, , 1/2 spin and even parity. Jaffe and 1/2 spin and even parity. Jaffe and Wilczek have suggested an underlying Wilczek have suggested an underlying quark model structure of this state[3]. quark model structure of this state[3]. There are other theoretical speculations There are other theoretical speculations which have predicted this state [3-6]. The which have predicted this state [3-6]. The rotational states of the S=+1 rotational states of the S=+1 ++ baryon baryon are shown in the paper by Akers[5].are shown in the paper by Akers[5].

A rotational spectrum is suggested for the + baryons based in calculations[5] and a rotational energy of 20 MeV .

[1] D. Diakonov, V. Petrov, and M. Polyakov, Z.Phys. A 359 , 305(1997).[2] R.L. Jaffe, SLAC-PUB-1774 Talk presented at thTopicalConf. on Baryon Resonances, Oxford, Eng.,Jul 5-9,1976;arXiv:hep-ph/0307341(2003).[3] M. Karliner and H.J. Lipkin, Phys. Lett. B,575 , 249 (2003).[4] J.Ellis, M.Karliner,M.Praszalowich, hep-ph/0401127(2004).[5] David Akers, arXiv.org:hep-ex/0310014(2004).

Summary of Positive Results

ICHEP 2004, Beijing, John Ellis, CERN

-(PBC) This experiment

-(HBC) experiment

Summary of Negative Results

ICHEP 2004, Beijing, John Ellis, CERN

A reliable identification of the above mentioned resonance needs to use 4-detectors and highprecision 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. In the momentum range, P > 0.900 GeV/c, protons couldn't be separated from other particles. Therefore, the experimental information has been analyzed similarly in two separate ranges.

2. Method

Beam

The events with V0 ( and Ks0) were

identified by using the following criteria [20-22]: 1) V0 stars from the photographs were selected according to -+p,Ks

0 -+ or e++e- hypothesis. A momentum limit of Ks

0 and is greater than 0.1 and 0.2 GeV/c, respectively ; 2) V0 stars should have the effective mass of or of Ks

0; 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 Ks

0 were appropriated events as .[20] G.N.Agakashiev et. al., Yad.Fiz.,1986,43(2),p.366,373.[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 Ks

0 decay. Distributions of and cos *

- were isotropic in the rest frame of Ks

0 when undivided Ks0

wereappropriated events as .

Identification and K0s

Figures (a,c) and (b,d) show the effective mass distribution of 8657-events with , 4122-events with Ks

0 particles and their 2 from kinematic fits, respectively. The expected functional form for 2 isdepicted 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 , Ks

0 are consistent with their PDG values. The effective mass of the + Ks

0p system, like that of the -+p system, has been measured with a precision of M+ /M + =1.1%. Then the effective mass resolution of + Ks

0p system was estimated to be on the average 0.6 % for identified protons with a momentum of 0.150 P 0.900 GeV/c. The preliminary estimate of the experimental total cross sections is equal to 3.8 ± 0.6 mb for Ks

0 production in the p+C collisions at 10 GeV/c.

The Ks0p effective mass distribution for 2300

combinations is shown in Figure. The solid curve is the sum of the background and 4 Breit-Wigner resonance curves.The total experimental background has been obtained by two 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 %. This distribution was fitted by the eight-order polynomial. The second of the randomly mixing method of the angle between Ks

0 and p for experimental events is described in [24]. Then, these background events were analyzed by using the same experimental condition and the effective mass distribution Ks

0p was fitted by the eight-order polynomial. The analysis done by two methods has shown that while fitting these distributions had the same coefficients and order of polynomial. The background for 0p combinations is estimated with FRITIOF model [25] and no more than 10 % has been obtained. No obvious structure in 0 p spectrum is seen in Figure. [24] V.L.Lyuboshits at al., JINR Rapid Comm., N6(74),p209, 1995.[25] FRITIOF, H. Pi, Comput. Phys.Commun. 71,173, 1992.[26]

3.Ks0p - spectrum analysis

3.1. Ks0p - spectrum for identified protons with

a momentum of 0.150 P 0.900 GeV/c

K

K

The Ks0p invariant mass spectrum shows

resonant structures with M = 1515 (5.3 s.d.) and 1700 MeV/c2(3.8 s.d.) in Figure. No obvious structure in mass regions of 1540,1610 and 1821 MeV/c2 is seen in Figure. The FRITIOF model shows that the average multiplicity in this range for all positive tracks, protons and + is equal to 1.2, 0.4 and 0.8, respectively. The background for Ks

0 + and Ks0 K+

combinations is equal to 46.6% and 4.4%, respectively. These observed peaks can be a reflection from resonances (1520) and (1700). The (n 0 ) invariant mass spectrum for events where + -meson was detected in reactions p+C3H8 +

0nX was detected and its mass was substituted by the mass of neutron.

3.3.Ks0p - spectrum with a momentum of

0.9 < P < 1.7 GeV/c

K

K

3.3.Ks0p - spectrum with a momentum of

pp 1.7 GeV/c

K

K

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 analysis done by two methods has shown that while fitting these distributions had the same coefficient and order of polynomial. The average multiplicity(FRITIOF) in this range for all positive tracks, protons and + is equal to 1.3, 0.8 and 0.5, respectively. Therefore the background for Ks

0 + and Ks

0 K+ ombinations is equal to 20% and 5%, respectively. The estimate of contribution for 0p combinations with FRITIOF model is equal to 8 %. No obvious structure in 0p spectrum is seen in figure. There are significant enhancements in mass regions of 1487, 1544, 1612 and 1805 MeV/c2 . Their excess above background is 3.0, 3.9,3.7 and 4.0 s.d.. There is a small peak in the mass region of 1685 MeV/c2 .

K

K

The sum of Ks0p - spectrum

The total Ks0p invariant mass distribution for

identified protons and positively charged tracks pp 1.7 GeV/c is shown in figure. The solid curve is the sum of the background and 4Breit-Wigner resonance curves. The background was fitted by the six-order polynomial. The total experimental background(dashed histogram) with the same experimental condition has been alsoobtained by the second method [21]. The dashed curve is the background taken in the form of a superposition of Legendre polynomials up to the 6 -th degree, inclusive. In figure, the below histogram shows the simulated background for the spectrum of 0p combinations. There are significant enhancements in mass regions of(1545±12), (1616 ± 10) and (1811 ± 11) MeVc2. Theirexcess above background by the second method is (5.5 ± 0.5), (4.8 ± 0.5) and (5.00 ±.6) S.D., respectively. There are small peaks in mass regions of 1680(3.6 s.d.) and 1980(3.0 s.d.) MeV/c2.

K

Conclusion

The effective mass spectra Ks0p 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 0.150 Pproton 0.900 GeV/c. The statistical significance in Table 1 is the based on the data from figure of the sumarry distribution. 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/c2. The primary total cross section for +(1540) production in p+C3H8 interactions is estimated to be 90 b. These experimental results for the rotational spectra of the + baryons are agreed with the calculated spectra from the theoretical report of D. Akers, arXiv.org:hep-ex/0310014, 2004 and with the experimental spectra from the report of Yu.A.Troyan et.al.,JINR, D1-2004-39, Dubna,2004.

Table 1. The effective mass spectra Ks0p have resulted in the

discovery of the peaks presented below

D. Akers, arXiv.org:hep-ex/0310014, 2004.

A mapping of the rotational spectra of the theta baryons is shown. The chartshows a grid of 70 MeV in the horizontal spacing and a mass separation in the vertical onthe order of the pion mass or 120 – 150 MeV . 1690

1487 1540 1610 18051690

- This experiment

Yu.A.Troyan et.al.,JINR, D1-2004-39, Dubna,2004;arXiv:hep-ex/0404003(2004).