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Search for Q + pentaquark at Belle

Search for Q + pentaquark at Belle. University of Ljubljana. hep-ex/0507014 submitted to PLB. B. Golob University of Ljubljana, Slovenia Belle Collaboration. KEKB and Belle detector Inclusive production of Q + Exclusive production of Q +. KEKB. Mt. Tsukuba. e -. KEKB. Belle.

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Search for Q + pentaquark at Belle

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  1. Search for Q+ pentaquark at Belle University of Ljubljana hep-ex/0507014 submitted to PLB B. Golob University of Ljubljana, Slovenia Belle Collaboration • KEKB andBelle detector • Inclusive production of Q+ • Exclusive production of Q+ B. Golob Pentaquark ‘05, Jefferson Lab, Oct 2005

  2. KEKB Mt. Tsukuba e- KEKB Belle diameter ~1 km e+ Integrated luminosity [pb-1] Oct‘05 Apr‘99 date KEKB: asymmetric B factory U(4s) p(e-)= 8.0 GeV/c p(e+)= 3.5 GeV/c ∫Ldt = 480 fb-1 Lpeak= 1.58x1034 s-1 cm-2 Presented analysis: ∫Ldt = 357 fb-1 B. Golob Pentaquark ‘05, Jefferson Lab, Oct 2005

  3. Belle detector Central Drift Chamber e+ 3.5 GeV 3(4) layer Si det. s(pt)/pt= 0.3% √pt2+1 e- 8 GeV Aerogel Cherenkov (n=1.015- 1.030) Particle ID e(K±)~85% e(p±→K±)<~10% @ p<3.5 GeV/c m and KL Counter (14/15 layers RPC+Fe) 1.5T SC solenoid EM calorimeter CsI (16X0) B. Golob Pentaquark ‘05, Jefferson Lab, Oct 2005

  4. Measurement method schematic view ( ) K0 K± p n K- Ks ds us uud udd us ds ds us primary K± momentum; ~500 MeV/c • kaons produced in e+e- annihilation as projectiles p • search for Q+(1540) in secondary interactions CDC K-,Ks SVD N in material X K±,Ks,KL • Selection: • 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); B. Golob Pentaquark ‘05, Jefferson Lab, Oct 2005

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

  6. Inclusive production of Q+ mass of secondary pK pK → L(1520) X → pK production inclusive ≡ analysis of m(pK-) and m(pKs); no suppression of inelastic reactions, no estimate of charge exchange K+n → pKs fit to threshold func.+ D-wave BW  resolution func. (4.02±0.08)x104L(1520) (±2.5 G) G and m consistent with PDG pK → L(1520) → pK formation, p(L) ~ 400 MeV/c 0.5% vtx’s with add. K KN →L(1520) X  B. Golob Pentaquark ‘05, Jefferson Lab, Oct 2005

  7. Inclusive production of Q+ fit m(pKs) to Gaussian + 3rd order polinomyal s~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-)= ½ B(L*→NK)= ½ (45±1)%; e’s from MC; B. Golob Pentaquark ‘05, Jefferson Lab, Oct 2005

  8. Exclusive production of Q+ • exclusive ≡ search for K+n → Q+ → pKs • motivated by DIANA result • Phys.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 ± 0.19 GQ+ = 0.9 ± 0.3 MeV B. Golob Pentaquark ‘05, Jefferson Lab, Oct 2005

  9. Exclusive production of Q+ K+ flux x-sect. material reconstr. efficiency no-rescattering nuclear prob. spectral func. 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 Nel K+n → pKsK+p → K+p B. Golob Pentaquark ‘05, Jefferson Lab, Oct 2005

  10. Exclusive production of Q+ process enabling a “counting” of K+p → pK+: p D*- → D0p- → (K+p-)D0p- K+ ratio Nch/Nel Material and nuclear effects mostly cancel out B. Golob Pentaquark ‘05, Jefferson Lab, Oct 2005

  11. Exclusive production of Q+ secondary vtx ( rSV ) • EK = EpK – EN • pK = f(EK,rSV,rIP) • pF = ppK - pK e+e- ineraction point ( rIP ) Solve iteratively for pK, pF reconstruction: p D*- → D0p- → (K+p-)D0p- K+ relations: • EN = mN - 2e - pF2/2mN K+ projectile e ~ 7 MeV; Sibirtsev et al., EPJ A23, 491(2005) B. Golob Pentaquark ‘05, Jefferson Lab, Oct 2005

  12. Exclusive production of Q+ pF for elastic events (D0), bkg. subtracted interact- ions on hydrogen NelD*= 470±26 selected (enhanced elastic reactions) DmD* from secondary pK+ pairs combined with additional pions in bins of m(pK+) NelD* = 21 ± 7 (Q+ mass) B. Golob Pentaquark ‘05, Jefferson Lab, Oct 2005

  13. Exclusive production of Q+ from ~20% of data uniform over running period from fit to published data; typical single experiment uncertainty from MC epKs/epK+= 0.43±0.05 sch/sel= 0.35±0.02 FK+/FK+D*= 850±20 (Q+ mass) B. Golob Pentaquark ‘05, Jefferson Lab, Oct 2005

  14. Exclusive production of Q+ Fit m(pKs) for possible Q+ signal yield at various m(pKs) and UL similar sensitivity as DIANA • no vtx’s with additional tracks • 50 MeV/c < pF < 300 MeV/c • 3rd order polynom.+signal (s=2 MeV/c2) DIANA: GQ+ = 0.9±0.3 MeV GQ+ < 0.64 MeV @ 90% C.L. B. Golob Pentaquark ‘05, Jefferson Lab, Oct 2005

  15. Summary • Q(1540)+ signal searched for using kaon secondary interactions • similar CM energy as in some positive result exp’s • inclusive search s(KN → Q(1540)+X)/s(KN → L(1520)X)<2.5% @90% C.L. • exclusive search • K+n → Q(1540)+ → p Ks yield normalized to total charge exchange K+n → p Ks • similar sensitivity to DIANA exp. • GQ+ < 0.64 MeV @90% C.L. for m(Q+)=1540 MeV/c2 • GQ+ < 1 MeV @90% C.L. for m(Q+)≤1570 MeV/c2 B. Golob Pentaquark ‘05, Jefferson Lab, Oct 2005

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

  17. L projectiles, backup Formation: Fitted parameters Of L(1520): m=1518.5±0.1 MeV/c2 G=13.5±0.4 MeV PDG: m=1519.5±1.0 MeV/c2 G=15.6±1.0 MeV • possible projectiles to produce L(1520): • K-, Ks, KL, L (?) • p(L)≥1.8 GeV/c (z≥0.35) to produce L(1520) • @29 GeV fraction L(z≥0.35) ~10% • s(e+e-→LX)~80 pb • s(e+e-→K0X)~470 pb • N(L)/N(K0) ~ 2% Tasso, PRD45, 3949 (1992) s(K-p→L(1520))~3 mb, s(Lp, total)~30mb assuming equal prod. rate of K0, K- • Lp→L(1520)X / Kp→L(1520)X ~ 10% (if s(Lp, total) saturated by L(1520)) L projectiles contribute few % to L(1520) production B. Golob Pentaquark ‘05, Jefferson Lab, Oct 2005

  18. Spectral function, backup Energy of nucleon within a nuclei; Eq = √q2+mN2 – U(q,r) U(q,r) – nuclear potential Fermi momentum ~300 MeV/c  Eq ≈ mN +q2/2mN - U(q,r) if U  1/r, virial theorem, U ~ -2 q2/2mN Eq ≈ mN -q2/2mN checks: use of Eq ≈ mN – 2e -q2/2mN, with fixed e gives - correct mD0 - expected pF distrib. use of Eq = mN – ER ER (removal energy) tuned to reproduce mD0 → ER=26 MeV ER= 2e +q2/2mN, nucleons with higher momenta are more tightly bound • Sibirtsev et al. • EPJ A23, 491(2005) • Z.Phys. A358, 357(1997) B. Golob Pentaquark ‘05, Jefferson Lab, Oct 2005

  19. Q+ exclusive – integrals, backup all quantities depending only on m(pK) → factorize • 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)) cancels in the ratio 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) remaining eff. dependence on p(pK) at given m(pK) B. Golob Pentaquark ‘05, Jefferson Lab, Oct 2005

  20. Q+ exclusive – integrals, backup ratio Nch/Nel MC integration; pF assumed isotropic w.r.t. pK; e(p(pK)) → 3% corr. to the ratio; uncertainty dominated by assumed EN, pF relation B. Golob Pentaquark ‘05, Jefferson Lab, Oct 2005

  21. pF distribution, backup Fit to (oscillator model) p0=115±4 MeV/c comparable to other measurements of pF, e.g. B.M. Abramov et al., JETP Lett. 71, 359(2000) using EN=mN hydrogen peak exactly at 0 B. Golob Pentaquark ‘05, Jefferson Lab, Oct 2005

  22. additional plots,backup sch/sel= 0.35±0.02 FK+/FK+D*= 850±20 NelD*=470±26 from fit to published data; typical single experiment uncertainty s=16 MeV/c2 major uncertainty from EN, pF relation Fit to m(pKs) sensitivity to GQ+ ±0.42 MeV epKs/epK+= 0.43±0.05 from Geant based MC; uncertainties in tracking and Ks eff., second. vtx eff., material desc., reaction kinem., MC stat. B. Golob Pentaquark ‘05, Jefferson Lab, Oct 2005

  23. GQ+, backup R.N. Cahn, G.H. Trilling, PRD69, 11501 (2004) BW form s(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 G estimate of 26 signal evts in two 5 MeV bins, bkg. level ~22 evts / bin assumed bkg. from charge exchange, sch=4.1±0.3 mb  I = (26/22) x 5 MeV x 4.1 mb = 24 mb MeV Bi=Bf=1/2 G=0.9±0.3 MeV B. Golob Pentaquark ‘05, Jefferson Lab, Oct 2005

  24. Ks,KL p → Q+ → p Ks, backup A. 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 Ks interference between amplitudes for same final state can 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 B. Golob Pentaquark ‘05, Jefferson Lab, Oct 2005

  25. Other S states, backup look for S(1670) 4* resonance m=1665-1685 (≈1670) MeV/c2 G=40-80 (≈60) MeV Fit m(pKs) to sum of 3rd order polyn.+ D-wave BW N(S(1670))=(2.4±1.3)x103 S(1670)/L(1520) < 2 @90% C.L. assuming B(L*→pK-)= ½ B(L*→NK)= ½ (45±1)%; B(S(1670)→pK0)=10% mass of secondary pK total s(pK-) shows two prominent structures at 1520 MeV/c2 and at ~1800 MeV/c2; latter due to several overllapingL and S states; clearly seen, hard to interpret B. Golob Pentaquark ‘05, Jefferson Lab, Oct 2005

  26. Some additional statistics, backup 95% C.L. limits: GQ+ < 0.78 MeV (@ 1539 MeV/c2) < 1.11 MeV (wide range) probability of stat. fluctuation for the signal of the DIANA size to the level observed by BELLE ~3% B. Golob Pentaquark ‘05, Jefferson Lab, Oct 2005

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