Search for Q+ pentaquark at Belle KEKB and Belle detector Inclusive production of Q+ Exclusive production of Q+ B. GolobUniversity of Ljubljana, SloveniaBelle CollaborationUniversity ofLjubljanahep-ex/0507014submitted to PLB

KEKBKEKB: asymmetricB factoryU(4s)p(e+)=3.5 GeV/cp(e-)=8.0 GeV/cLdt = 480 fb-1Lpeak = 1.58x1034 s-1 cm-2Presented analysis:Ldt = 357 fb-1

Belle detector3(4) layerSi det.Central Drift ChamberAerogelCherenkov(n=1.015- 1.030)1.5T SC solenoide-8 GeVe+3.5 GeVEM calorimeterCsI (16X0)m and KLCounter(14/15 layersRPC+Fe)s(pt)/pt= 0.3% pt2+1Particle IDe(K)~85% e(pK)

Measurement method kaons produced in e+e- annihilation as projectiles search for Q+(1540) in secondary interactionsSVDCDCSelection:

identified p, K; not from IP (dr>0.1 cm);

Ks -> p+p-; detached vtx, not from IP (dr>0.1 cm), 3s within m(Ks)

pK detached vtx (1 cm < r < 11 cm);pK-,KsK,Ks,KLN inmaterialX

Measurement method(x,y) coord. of pKs secondary vertices => detector tomographypK pairs arising from interactions with nucleonsin detector material

Inclusive production of Q+inclusive analysis of m(pK-) and m(pKs);no suppression of inelastic reactions, no estimate of charge exchange K+n pKsfit to threshold func.+D-wave BW resolution func.(4.020.08)x104 L(1520) (2.5 G)G and m consistent with PDGpK L(1520) pKformation,p(L) ~ 400 MeV/c0.5% vtxswith add. K

KN L(1520) X

Inclusive production of Q+fit m(pKs) to Gaussian + 3rd order polinomyals~2 MeV/c2 from MC + small corr. from W- L K-< 2.5% @ 90% C.L.assuming B(Q+pKs)=25%;using B(L*pK-)= B(L*NK)= (451)%;es from MC;

Exp.processE[GeV]s(Q+)/s(L*)CDFppQ+X1960

Exclusive production of Q+exclusive search for K+n Q+ pKs

motivated by DIANA resultPhys.Atom.Nucl. 66, 1715 (2003)

main steps

suppression of inelastic reactions (additional p0 or unrec. p+ major bkg.; also contributions from Ks,Lp pKs) normalize to charge exchange K+n pKs(Nch)

Nch indirectly from elastic K+p K+p (Nel)

interpretation NQ+/Nch GQ+ Cahn, Trilling, PRD69, 11501 (2004)NQ+/Nch = 0.66 0.19GQ+ = 0.9 0.3 MeV

Exclusive production of Q+number of charge exchange events:MC may not reproduce M and e accurately enough;P and S model dependent;use data and estimate Nch relative to NelK+n pKs K+p K+p

Exclusive production of Q+D*- D0p- (K+p-)D0 p-pK+ratio Nch/NelMaterial and nuclear effects mostly cancel outprocess enabling a counting of K+p pK+:

Exclusive production of Q+reconstruction:D*- D0p- (K+p-)D0 p-pK+K+ projectile EN = mN - 2e - pF2/2mNe ~ 7 MeV; Sibirtsev et al., EPJ A23, 491(2005)relations:

Exclusive production of Q+DmD* from secondary pK+ pairs combined with additional pionsNelD*=47026pF for elastic events (D0), bkg.subtractedinteract-ions on hydrogenin binsof m(pK+)NelD* = 21 7 (Q+ mass) selected(enhancedelasticreactions)

Exclusive production of Q+FK+/FK+D*= 85020(Q+ mass) sch/sel= 0.350.02from fit to publisheddata; typical singleexperiment uncertaintyfrom MCfrom ~20% of datauniform overrunning periodepKs/epK+=0.430.05

Exclusive production of Q+Fit m(pKs) for possibleQ+ signal no vtxs with additional tracks 50 MeV/c < pF < 300 MeV/c 3rd order polynom.+signal (s=2 MeV/c2) yield at various m(pKs)and ULsimilar sensitivity as DIANAGQ+ < 0.64 MeV @ 90% C.L.DIANA: GQ+ = 0.90.3 MeV

Summary Q(1540)+ signal searched for using kaon secondary interactions similar CM energy as in some positive result exps

inclusive search s(KN Q(1540)+X)/s(KN L(1520)X)

Selection details, backupPIDp: Lp/K > 0.6, Lp/p > 0.6K: LK/p > 0.6, LK/p > 0.6not identified as eL: likelihood based on CDC, ACC, TOF

Ksp+p- 10 MeV (3s) from m(Ks)zdist at vtx < 1 cmdr of daughters > 0.1 cmq(p(Ks), r(vtx,IP)) < 90o

pK vtxdr(p,K) > 0.1 cmzdist at vtx < 1 cmq(p(pK), r(vtx,IP)) < 90o

other50 MeV/c < pF < 300 MeV/cd/R > 0.1 (d dist. to nearest track, R radial coordinate of vtx)angular cuts (DIANA)do not improveS/N or sensitivityafter the pF selectionapplied (suppression of 1.2, e=93% significance ~1.02)typical resolutionon sec. vtx~400 mm (r)

L projectiles, backupFormation:possible projectiles to produce L(1520):K-, Ks, KL, L (?)

p(L)1.8 GeV/c (z0.35) to produce L(1520)@29 GeV fraction L(z0.35) ~10%s(e+e-LX)~80 pbs(e+e-K0X)~470 pbN(L)/N(K0) ~ 2%Tasso, PRD45, 3949 (1992)

s(K-pL(1520))~3 mb, s(Lp, total)~30mbassuming equal prod. rate of K0, K- LpL(1520)X / KpL(1520)X ~ 10% (if s(Lp, total) saturated by L(1520))L projectiles contribute few %to L(1520) productionFitted parametersOf L(1520):m=1518.50.1 MeV/c2G=13.50.4 MeVPDG:m=1519.51.0 MeV/c2G=15.61.0 MeV

Spectral function, backupEnergy of nucleon within a nuclei;Eq = q2+mN2 U(q,r)U(q,r) nuclear potentialFermi momentum ~300 MeV/c Eq mN + q2/2mN - U(q,r)

if U 1/r, virial theorem, U ~ -2 q2/2mNEq mN - q2/2mN

checks: use of Eq mN 2e - q2/2mN, with fixed egives - correct mD0- expected pF distrib.

use of Eq = mN ERER (removal energy)tuned to reproduce mD0 ER=26 MeVER= 2e + q2/2mN, nucleons with higher momenta are more tightly boundSibirtsev et al.EPJ A23, 491(2005)Z.Phys. A358, 357(1997)

Q+ exclusive integrals, backup products Me approx. independent of q decoupled from F fraction of recon. D* in pF hydrogen peak w.r.t. all ~independent of p(pK); since fraction 1/P P ~ F(p(pK))all quantities depending only on m(pK) factorizecancels in theratioremaining eff. dependenceon p(pK) at given m(pK)S(EN,pF) = W(pF)d(EN-f(pF));W(pF) Fermi mom. distrib. (data);f(pF) defined so that EN = f(pF) max. of S(EN,pF)

Q+ exclusive integrals, backupratio Nch/NelMC integration; pF assumed isotropic w.r.t. pK;e(p(pK)) 3% corr. to the ratio;uncertainty dominated by assumed EN, pF relation

pF distribution, backupFit top0=1154 MeV/ccomparable to other measurements of pF,e.g. B.M. Abramov et al., JETP Lett. 71, 359(2000)(oscillator model)using EN=mN hydrogen peak exactly at 0

additional plots , backupmajor uncertainty from EN, pF relationFK+/FK+D*= 85020sch/sel= 0.350.02from fit to publisheddata; typical singleexperiment uncertaintyNelD*=47026s=16 MeV/c2epKs/epK+=0.430.05from Geant based MC;uncertainties in tracking and Ks eff.,second. vtx eff., material desc., reaction kinem., MC stat.Fit tom(pKs)

sensitivityto GQ+0.42 MeV

GQ+, backupR.N. Cahn, G.H. Trilling, PRD69, 11501 (2004) BW forms(m) = BiBfs0[G2/4] / [(m-m0)2+G2/4]s0=68 mb (J=1/2)mass resolution broader than natural width integral I= s(m) dm = 107 mb BiBf Gestimate of 26 signal evts in two 5 MeV bins, bkg. level ~22 evts / binassumed bkg. from charge exchange, sch=4.10.3 mb I = (26/22) x 5 MeV x 4.1 mb = 24 mb MeV

Bi=Bf=1/2

G=0.90.3 MeV

Ks,KL p Q+ p Ks, backupA. Kaidalov, private comm.apart from charge exchange reactions also Ks p Ks p and KL p Ks p may contribute to signal

KL p Q+ p Ksinterference between amplitudes for same final statecan lead to hole in s(KL p, total) due to Q+

s(KL p, total) ~ 2 mb negative interference < 1 mb(also depending on decay angles)s(K+ n Q+ p Ks) ~ 17 mb (DIANA)hole negligible

Ks p Q+ p Ks would also compensate for that

Other S states, backuptotal s(pK-) showstwo prominent structures at 1520 MeV/c2 and at ~1800 MeV/c2;latter due to several overllaping L and S states;clearly seen, hard to interpret

Some additional statistics, backup95% C.L. limits:GQ+ < 0.78 MeV (@ 1539 MeV/c2) < 1.11 MeV (wide range)

probability of stat. fluctuationfor the signal of the DIANA size to the level observed by BELLE ~3%