B. Golob Pentaquark ‘05, Jefferson Lab, Oct 2005 Search for  + pentaquark at Belle KEKB and Belle detector Inclusive production of  + Exclusive production of  + B. Golob University of Ljubljana, Slovenia Belle Collaboration University of Ljubljana hep-ex/ submitted to PLB

B. Golob Pentaquark ‘05, Jefferson Lab, Oct 2005 Integrated luminosity [pb -1 ] date Apr‘99 Oct‘05 KEKB KEKB: asymmetric B factory diameter ~1 km Mt. Tsukuba KEKB Belle  (4s) e+e+ e-e- p(e + )= 3.5 GeV/c p(e - )= 8.0 GeV/c ∫Ldt = 480 fb -1 L peak = 1.58x10 34 s -1 cm -2 Presented analysis: ∫Ldt = 357 fb -1

B. Golob Pentaquark ‘05, Jefferson Lab, Oct 2005 Belle detector 3(4) layer Si det. Central Drift Chamber Aerogel Cherenkov (n= ) 1.5T SC solenoid e - 8 GeV e GeV EM calorimeter CsI (16X 0 )  and K L Counter (14/15 layers RPC+Fe)  (p t )/p t = 0.3% √p t 2 +1 Particle ID  (K ± )~85%  (  ± →K ± p<3.5 GeV/c

B. Golob Pentaquark ‘05, Jefferson Lab, Oct 2005 Measurement method schematic view  kaons produced in e + e - annihilation as projectiles  search for  + (1540) in secondary interactions SVD CDC Selection:  identified p, K ± ; not from IP (  r>0.1 cm);  K s ->  +  - ; detached vtx, not from IP (  r>0.1 cm), 3  within m(K s )  pK detached vtx (1 cm < r < 11 cm); p K -,K s K ±,K s,K L N in material K 0 K ± p n K - K s ds us uud udd us ds ds us ( ) X primary K ± momentum; ~500 MeV/c

B. Golob Pentaquark ‘05, Jefferson Lab, Oct 2005 Measurement method (x,y) coord. of pK s secondary vertices => detector “tomography” pK pairs arising from interactions with nucleons in detector material

B. Golob Pentaquark ‘05, Jefferson Lab, Oct 2005 Inclusive production of  + inclusive ≡ analysis of m(pK - ) and m(pK s ); no suppression of inelastic reactions, no estimate of charge exchange K + n → pK s mass of secondary pK fit to threshold func.+ D-wave BW  resolution func. (4.02±0.08)x10 4  (1520) (±2.5  )  and m consistent with PDG pK →  (1520) → pK formation, p(  ) ~ 400 MeV/c pK →  (1520) X → pK production 0.5% vtx’s with add. K  →  (1520) X 

B. Golob Pentaquark ‘05, Jefferson Lab, Oct 2005 Inclusive production of  + fit m(pK s ) to Gaussian + 3rd order polinomyal  ~2 MeV/c 2 from MC + small corr. from  - →  K- < 90% C.L. assuming B(  + →pK s )=25%; using B(  *→pK - )= ½ B(  *→NK)= ½ (45±1)%;  ’s from MC; Exp.processE[GeV]  (  + )/  (  *) CDF pp→  + X 1960<3% HERA-B pA→  + X 42<2% SPHINX pA→  + X 12<2% Belle KA→  + X ~2<2.5% LEPS  A→  + X ~2~60% HERMES eD→  + X 7~200%

B. Golob Pentaquark ‘05, Jefferson Lab, Oct 2005 Exclusive production of  + exclusive ≡ search for K + n →  + → pK s motivated by DIANA result Phys.Atom.Nucl. 66, 1715 (2003) main steps  suppression of inelastic reactions (additional  0 or unrec.  + major bkg.; also contributions from K s,L p → pK s )  normalize to charge exchange K + n → pK s (N ch )  N ch indirectly from elastic K + p → K + p (N el )  interpretation N  + /N ch    + Cahn, Trilling, PRD69, (2004) N  + /N ch = 0.66 ± 0.19   + = 0.9 ± 0.3 MeV

B. Golob Pentaquark ‘05, Jefferson Lab, Oct 2005 Exclusive production of  + number of charge exchange events: K + flux x-sect. material reconstr. efficiency no-rescattering nuclear prob. spectral func. MC may not reproduce M and  accurately enough; P and S model dependent; use data and estimate N ch relative to N el K + n → pK s K + p → K + p

B. Golob Pentaquark ‘05, Jefferson Lab, Oct 2005 Exclusive production of  + D* - → D 0  - → (K +  - ) D0  - p K+K+ ratio N ch /N el Material and nuclear effects mostly cancel out process enabling a “counting” of K + p → pK + :

B. Golob Pentaquark ‘05, Jefferson Lab, Oct 2005  E K = E pK – E N  p K = f(E K,r SV,r IP )  p F = p pK - p K Exclusive production of  + reconstruction: D* - → D 0  - → (K +  - ) D0  - p K+K+ K + projectile  E N = m N - 2  - p F 2 /2m N  ~ 7 MeV; Sibirtsev et al., EPJ A23, 491(2005) relations: e + e - ineraction point ( r IP ) secondary vtx ( r SV ) Solve iteratively for p K, p F

B. Golob Pentaquark ‘05, Jefferson Lab, Oct 2005 Exclusive production of  +  m D* from secondary pK + pairs combined with additional pions N el D* = 470±26 p F for elastic events (D 0 ), bkg. subtracted interact- ions on hydrogen in bins of m(pK + ) N el D* = 21 ± 7 (   mass) selected (enhanced elastic reactions)

B. Golob Pentaquark ‘05, Jefferson Lab, Oct 2005 Exclusive production of  +  K+ /  K+ D* = 850±20 (   mass)  ch /  el = 0.35±0.02 from fit to published data; typical single experiment uncertainty from MC from ~20% of data uniform over running period  pKs /  pK+ = 0.43±0.05

B. Golob Pentaquark ‘05, Jefferson Lab, Oct 2005 Exclusive production of  + Fit m(pK s ) for possible  + signal  no vtx’s with additional tracks  50 MeV/c < p F < 300 MeV/c  3rd order polynom.+signal (  =2 MeV/c 2 ) yield at various m(pK s ) and UL similar sensitivity as DIANA   + < % C.L. DIANA:   + = 0.9±0.3 MeV

B. Golob Pentaquark ‘05, Jefferson Lab, Oct 2005 Summary   (1540) + signal searched for using kaon secondary interactions  similar CM energy as in some positive result exp’s  inclusive search  (KN →  (1540) + X)/  (KN →  C.L.  exclusive search  K + n →  (1540) + → p K s yield normalized to total charge exchange K + n → p K s  similar sensitivity to DIANA exp.    + < 0.64 C.L. for m(  + )=1540 MeV/c 2    + < 1 C.L. for m(  + )≤1570 MeV/c 2

B. Golob Pentaquark ‘05, Jefferson Lab, Oct 2005 Selection details, backup PID  p: L p/K > 0.6, L p/  > 0.6  K±: L K/p > 0.6, L K/p > 0.6  not identified as e ±  L: likelihood based on CDC, ACC, TOF K s   +  - ±10 MeV (3  ) from m(K s )  z dist at vtx < 1 cm   r of daughters > 0.1 cm   (p(K s ), r(vtx,IP)) < 90 o pK vtx   r(p,K ± ) > 0.1 cm  z dist at vtx < 1 cm   (p(pK), r(vtx,IP)) < 90 o other  50 MeV/c < p F < 300 MeV/c  d/R > 0.1 (d – dist. to nearest track, R – radial coordinate of vtx) angular cuts (DIANA) do not improve S/N or sensitivity after the p F selection applied (suppression of 1.2,  =93%  significance ~1.02) typical resolution on sec. vtx ~400  m (r)

B. Golob Pentaquark ‘05, Jefferson Lab, Oct 2005  projectiles, backup Formation: possible projectiles to produce  (1520): K -, K s, K L,  (?) p(  )≥1.8 GeV/c (z≥0.35) to produce  GeV fraction  (z≥0.35) ~10%  (e + e - →  X)~80 pb  (e + e - →K 0 X)~470 pb  N(  )/N(K 0 ) ~ 2% Tasso, PRD45, 3949 (1992)  (K - p→  (1520))~3 mb,  (  p, total)~30mb assuming equal prod. rate of K 0, K -  p→  (1520)X / Kp→  (1520)X ~ 10% (if  (  p, total) saturated by  (1520))  projectiles contribute few % to  (1520) production Fitted parameters Of  (1520): m=1518.5±0.1 MeV/c 2  =13.5±0.4 MeV PDG: m=1519.5±1.0 MeV/c 2  =15.6±1.0 MeV

B. Golob Pentaquark ‘05, Jefferson Lab, Oct 2005 Spectral function, backup Energy of nucleon within a nuclei; E q = √q 2 +m N 2 – U(q,  ) U(q,  ) – nuclear potential Fermi momentum ~300 MeV/c  E q ≈ m N + q 2 /2m N - U(q,  ) if U  1/r, virial theorem, U ~ -2 q 2 /2m N E q ≈ m N - q 2 /2m N checks: use of E q ≈ m N – 2  - q 2 /2m N, with fixed  gives - correct m D0 - expected p F distrib. use of E q = m N – E R E R (removal energy) tuned to reproduce m D0 → E R =26 MeV E R = 2  + q 2 /2m N, nucleons with higher momenta are more tightly bound A.Sibirtsev et al. EPJ A23, 491(2005) Z.Phys. A358, 357(1997)

B. Golob Pentaquark ‘05, Jefferson Lab, Oct 2005  + exclusive – integrals, backup  products M  approx. independent of  → decoupled from   fraction of recon. D* in p F 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) → factorize cancels in the ratio remaining eff. dependence on p(pK) at given m(pK) S(E N,p F ) = W(p F )  (E N -f(p F )); W(p F ) Fermi mom. distrib. (data); f(p F ) defined so that E N = f(p F )  max. of S(E N,p F )

B. Golob Pentaquark ‘05, Jefferson Lab, Oct 2005  + exclusive – integrals, backup ratio N ch /N el MC integration; p F assumed isotropic w.r.t. p K ;  (p(pK)) → 3% corr. to the ratio; uncertainty dominated by assumed E N, p F relation

B. Golob Pentaquark ‘05, Jefferson Lab, Oct 2005 p F distribution, backup Fit to p 0 =115±4 MeV/c comparable to other measurements of p F, e.g. B.M. Abramov et al., JETP Lett. 71, 359(2000) (oscillator model) using E N =m N  hydrogen peak exactly at 0

B. Golob Pentaquark ‘05, Jefferson Lab, Oct 2005 additional plots, backup major uncertainty from E N, p F relation  K+ /  K+ D* = 850±20  ch /  el = 0.35±0.02 from fit to published data; typical single experiment uncertainty N el D* =470±26  =16 MeV/c 2  pKs /  pK+ = 0.43±0.05 from Geant based MC; uncertainties in tracking and K s eff., second. vtx eff., material desc., reaction kinem., MC stat. Fit to m(pK s ) sensitivity to   + ±0.42 MeV

B. Golob Pentaquark ‘05, Jefferson Lab, Oct 2005   +, backup R.N. Cahn, G.H. Trilling, PRD69, (2004) BW form  (m) = B i B f  0 [  2 /4] / [(m-m 0 ) 2 +  2 /4]  0 =68 mb (J=1/2) mass resolution broader than natural width  integral I=∫  (m) dm = 107 mb B i B f  estimate of 26 signal evts in two 5 MeV bins, bkg. level ~22 evts / bin assumed bkg. from charge exchange,  ch =4.1±0.3 mb  I = (26/22) x 5 MeV x 4.1 mb = 24 mb MeV B i =B f =1/2  =0.9±0.3 MeV

B. Golob Pentaquark ‘05, Jefferson Lab, Oct 2005 Ks,K L p →  + → p K s, backup A. Kaidalov, private comm. apart from charge exchange reactions also K s p → K s p and K L p → K s p may contribute to signal K L p →  + → p K s interference between amplitudes for same final state can lead to “hole” in  (K L p, total) due to  +  (K L p, total) ~ 2 mb  negative interference < 1 mb (also depending on decay angles)  (K + n →  + → p K s ) ~ 17 mb (DIANA) “hole” negligible K s p →  + → p K s would also compensate for that

B. Golob Pentaquark ‘05, Jefferson Lab, Oct 2005 Other  states, backup mass of secondary pK total  (pK - ) shows two prominent structures at 1520 MeV/c 2 and at ~1800 MeV/c 2 ; latter due to several overllaping  and  states; clearly seen, hard to interpret look for  (1670) 4* resonance m= (≈1670) MeV/c2  =40-80 (≈60) MeV Fit m(pK s ) to sum of 3rd order polyn.+ D-wave BW N(  (1670))=(2.4±1.3)x10 3  (1670)/  (1520) < C.L. assuming B(  *→pK - )= ½ B(  *→NK)= ½ (45±1)%; B(  (1670)→pK 0 )=10%

B. Golob Pentaquark ‘05, Jefferson Lab, Oct 2005 Some additional statistics, backup 95% C.L. limits:   + < 0.78 MeV 1539 MeV/c 2 ) < 1.11 MeV (wide range) probability of stat. fluctuation for the signal of the DIANA size to the level observed by BELLE ~3%