Pentaquark Searches at BaBar. Tetiana Berger-Hryn ova, SLAC For the BaBar Collaboration

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1 Pentaquark Searches at BaBar Tetiana Berger-Hryn ova, SLAC For the BaBar Collaboration

2 Outline Search for Θ + in Electro- and Hadro- Production Inclusive Search for Strange-Pentaquark Production in e + e - Annihilation Inclusive Search for anti-charm Pentaquark Production in e + e - Annihilation Search for Θ *++ (pk + ) in B decay to the p K + final state 2

3 PEP-II is an asymmetric e + e - collider with a CM energy of 1.58 GeV. Peak luminosity = cm -2 s -1 Integrated luminosity = ~31 fb -1 BaBar/PEP-II BaBar DIRC Fused Silica Cherenkov radiator Covers 8% of solid angle Particle ID above 6 MeV/c Cherenkov Angle (Kaon from D* + D π +, D K - π + sample) BaBar SVT 5 layers of double-sided Silicon strip sensors. All Events BaBar EMC 658 CsI(Tl) crystals E resolution ~2 % at high E. BaBar DCH 4 layers, axial and stereo wires. Covers 92% of solid angle δp t /p t ~ % Particle ID up to 1.3 GeV/c 3

4 Search for Θ + in Electro- & Hadro- Production 4

5 Electro- and Hadro-Production Evidence of Θ + found in: real/virtual photoproduction (*) hadroproduction on hydrogen or nuclear target No signal in CLAS: ~6x more data! ~4x more data! Study Θ + pk S production in interactions with the material of the BABAR inner detector! Hadroproduction: interactions of hadrons produced in e + e - annihilation with detector material Electroproduction: off-beam e - and e + bent into beampipe (Be) in horizontal plane Compare with BABAR results Interaction Region 5

6 pk s reconstruction/detector Material Preliminary 233 fb -1 e + e data DOCA < 3 mm K S FL > 2 mm pk S Vertex K S π π + SB Signal region (SR Sideband (SB) p SVT 6

7 Detector Tomography with pk s Vertices Preliminary 233 fb -1 e + e data SVT e - e + SVT support tube DCH inner wall beampipe Ta -.2 < y <.7 cm -3.1< x < -2.2 cm Fe z profile e- side Be Ta 7

8 pk S Mass Distribution Preliminary 233 fb -1 e + e data SB K S Mass Distribution Signal region (SR) Sideband (SB) All vertices (e- and h-production) SR No Θ + signal SB Vertices from e - Be interaction (e-production) SR No Θ + signal SB M(K S p)/gev/c 2 Remove candidates with associated baryons (p,,d,t) Look for other associated tracks p,p,d,t; π ±, K ± π K S π + p 8

9 Preliminary 233 fb -1 e + e data Association of π ±, K ± with (p, K s ) Vtx K +* (892) SR SB events with p K S π + All vertices (same for e - Be with fewer events) K s π + Λ(152) SR SB events with p K S K pk - No Θ + signal No Θ + signal SR-SB removed K +* (892) SB SR 9

10 e - Be Electroproduction Preliminary 233 fb -1 e + e data HERMES (e + d K S p + X) ZEUS (e - p e - K S p + X M=1528±3 MeV ~5σ Σ * (148) M=1522±3 MeV ~5σ Possible acceptance loss in low mass region: (PID requires p(p) >4.1 GeV/c; p(k S )>3 GeV/c) Fit uses Σ * (148) [PDG 1star] 1

11 e + e - Inclusive Pentaquark Searches 11

12 Exotic resonances: Θ +, seen by several and Ξ 5,-- seen by one experiments. Fits into several models;1+8 multiplet of SU(3) f is favored. Production could be similar to baryons of same mass. Entries / 7.5 MeV/c Overview NA a) b) M(Ξπ) [GeV/c 2 ] Events / 2 MeV/c 2 Θ + ududs pk S CLAS M(nK + ) (GeV/c 2 ) M(nK + ) (GeV/c 2 ) N 5 udd(uu,ss) N 5+ uud(dd,ss) ΛK S, Σ K S ΛK +, Σ K + Σ 5 uds(u,d,s ) Σ 5- dds(uu,ss) Σ 5+ uus(dd,ss) pk S Ξ -- 5 sdsdu Ξ 5- dss(uu,dd) Ξ 5 uss(uu,dd) Ξ 5+ ususd 12 Ξ π - ΛK -, Σ K - ΛK S, Σ K S

13 Search for Θ + /Σ 5+ pk S 123 fb -1 PRL 95, 422 (25) Proton selection using de/dx and Cherenkov, clean over wide momentum range. Use K S π+ π. 3x1 6 reconstructed decays Expected Resolution (HWHM) on Θ + mass ~ 2 MeV (from MC) Can also look for Σ 5+. Upper Limits of total cross section: Θ + +Θ - : for Γ=1(8)MeV 171(363)fb Candidates/ (2 MeV/c 2 ) ~98K Λ C s in data sample Resolution 5-7 MeV at Λ C mass 1 3 No Σ

14 Search for Ξ 5 /-- Ξ - π ± IP π Ξ Λ π Λ π Ξ p + Geometrical selection of two displaced vertices Good p and π selection (de/dx, θ c ) Select masses near the nominal Λ and Ξ - masses Control signals: Ξ * (153) Ξ - π +, Ξ c (247) Ξ - π + No signal of Ξ 5 / Ξ 5 -- PRL 95, 422 (25) 24, entries 8 entries Mass resolution ~8 MeV/c 2 in Ξ 5 region (r.m.s) U. L. on total cross section: Ξ Ξ 5 -- : for Γ=1(18)MeV 25(36) fb 14

15 Search for Ξ 5 /N 5 ΛK S π π + π p + Entries per 2 MeV 8 6 N 5 1 Ξ c 123fb -1 hep-ex/4864 ΛK S K s Λ Λ 2 - p* < 3 GeV - p* > 3 GeV (scale 1) (GeV) m Λ K S Μ pπ [GeV] K S Entries per 2 MeV No Ξ 5 signal Ξ C N Ξc 11 σ = 5.9 MeV Μ ππ ππ [GeV] (GeV) m Λ K S

16 Search for N 5+ Λ K +, Ξ 5- Λ K - Entries per 2 MeV N fb -1 hep-ex/ Λ c feed-down + Λ c - p* < 3 GeV - p* > 3 GeV (scale 1) ΛK + Entries per 2 MeV Ω - p* < 3 GeV - p* > 3 GeV (scale 1) ΛK Entries per 2 MeV (GeV) DATA N N = Λc 6 + σ = Λc RMS 5.3 = 5.3 MeV Λ c+ Cabibbo- Suppressed Decay (GeV) m Λ + K m Λ + K N Ω 63 σ = 3. MeV (GeV) Ω Entries per 1 MeV No Ξ 5 signal m Λ K (GeV) m Λ K - 16

17 Search for N 5+ /Ξ 5- Σ K ±, Ξ 5 /N 5 Σ K s + Σ K Σ K 123 fb -1 hep-ex/4864 Σ K s p*>3 GeV 1<p*<2 GeV No N 5+ signal No Ξ 5- signal No Ξ 5 /N 5 signal 17

18 Results (e + e - Annihilations) No signal for any pentaquark state observed Assumptions J=1/2 BF(Θ + pk s )=25% BF(Ξ 5 -- Ξ - π + )=5% BF for Ξ 5- and Ξ 5 very unclear Intrinsic width 1-18 MeV/c 2 Limits on production times branching fraction 4-15x lower than production rates for conventional baryons 123 fb -1 PRL 95, 422 (25) 18

19 Θ c Pentaquark Search 15-plet C=+2 SU(4) 6-plet (cdcd ) C I anti plet C=+1 Ξ + (usus ) (cdsd ) Ξ (sdsd ) Y anti-decupltet (1) + octet (8) C= Θ + (udud ) anti-6-plet C=-1 Θ c (udud ) 19 D K - π + mode only

20 Search for Θ c pd* - ( (K + π,k + π π + π )π ) BaBar Preliminary 123 fb -1 e + e data, see hep-ex/5144 for details Reconstruct ~75k of D *- D *- ( K + π ) After cuts ~55k D *- ~4k bkgr After cuts ~73k D *- ~62k bkgr with proton requirement D *- ( K + π π + π ) Expected Resolution (HWHM) on Θ c mass ~ 3 MeV (from MC) 2

21 Θ *++ Pentaquark Search in B-decay 21

22 Current Status Theory: Θ *++ K + p mode dominant m Θ*++ = GeV/c 2 & Γ Θ*++ = MeV uddd ddds uddd uudd uuud ddss dsss Not seen by CLAS, HERMES, SAPHIR, ZEUS A hint from STAR? (at ~1.53GeV/c 2, Γ~2MeV); isospin partner not seen in BaBar inclusive search with ~3-1 times statistics In K + p scattering: no sign of Θ *++ ; constrains Γ(Θ* ++ )<15MeV Previous searches in B decays (idea: Phys.Lett.B, (24)) By-product of the B ± p K ± analysis, very low background uuud uuus uuss usss BaBar 81fb -1 [hep-ex/4837]: B(B + Θ *++ ) B(Θ *++ pk + )< 1.5 9% CL for narrow state with m(θ *++ )= GeV/c 2 BELLE 14fb -1 [Phys Lett B 617(25),141]: B(B + Θ *++ ) B(Θ *++ pk + )<.9 9% CL for narrow state at m(θ *++ )=1.71 GeV/c 2 [search region: ] Θ * Δ * X 1s X 2s Ω * 22

23 Analysis Overview Data Samples 21 fb -1 on the ϒ(4S) resonance (232 M B ± mesons) B + u W + d u u u Θ *++ Isolate B ± p K ± final state, search for Θ *++ in m pk+ B decay Major Backgrounds: Baryons from e + e - q, where q=u,d,s,c (suppress topologically) Allowed B decays: B ± XK ±, X p (X=η c,j/ψ,χ c,ψ(2s)) B + u e + e - PRD 72, 5111(R) 25 d u u q e + e - Θ *++ 23

24 B signal B ppk Dalitz Plot E * B-E * B expected η c m p ~m B J/ψ p K + signal box 78 events: ~566±29 signal events ~ 22±5 combinatorial background Sideband: 1661 events Θ *++ region ψ(2s) χ c[-2] 24

25 Events with 2.85<m pp <3.15GeV/c 2 Events with 2.85>m pp GeV/c 2 & m pp >3.15GeV/c 2 Θ *++ Search (PRD 72, 5111(R) 25) For m pk+ <3GeV/c 2 : σ pk+ varies from 1-3MeV/c 2 and ε av =2.5±.1% Remove from UL calculation assuming narrow (<1GeV) Θ*++ resonance! 25

26 Conclusions BaBar Pentaquark searches have yielded negative results High statistics, excellent mass resolution: Hadro- and Electro-Production in Detector Material No Θ + pk s found Inclusive Search in e + e - Annihilations No evidence found for eight members of strange anti-decuplet and octet, and anti-charm Θ c Limits below expectation for baryons (factor 1-15) for Θ +, Ξ 5 -- Low statistics/low background, excellent mass resolution: No Θ *++ observed in B + p K + : limit set on product of BF Pentaquark Searches highlight potential for study of charmed and non-charmed Baryons at BaBar 26

27 Backup Slides

28 p and K s Samples Clean samples of selected p and K s π + π - candidates Sideband Signal region (SR) Sideband (SB) S/B Very good S/B behaviour with flight length flight length [cm] lab. momentum of K S lab. momentum of p 28

29 Combine p or K S with identified π - or K + SR K* - (892) π Remove K * (892) SR-SB SB π No Θ + Seen π Κ + SR Λ(1115) SR SB SB 29

30 Zeus Comparison 3

31 Upper Limits for Production Cross Section Sample Bin: 3. GeV < p* < 3.5 GeV yield 95% CL on production Xsection: Γ= 1 Γ = 8 MeV < < fb < 5.4x1-5 < 1.7x1-5 per q event < 17.9x1-5 < 35.x1-5 per ϒ(4S) 31

32 Search for Θ c 32

33 Hints of a signal? d-au Bkgr subtracted Candidates/ (5MeV/c 2 ) 1 3 STAR d-au pk + and K - d-au at 2GeV combinatorial & correlated pairs m pk+, GeV/c 2 STAR Preliminary Θ ++? Au-Au Bkgr subtracted Suppressed Zero! Θ ++? From Volker D Burkert s talk at LP5 33 Puzzle: BaBar didn t observe the Θ *++ isovector partner Θ *+ in the search of Tetiana pk Berger-Hryn'ova S resonances

34 e + e - q Background Suppression e + e - B decay q e + e - Background 94% Signal MC 67% L L = * i * i (3cos 2 B, i = i i p p, 2 θ Thr 1) 2, (i = photons and tracks which are not part of the B ppk ) and angles between the B ppk thrust (momentum) and z axis combined into Fisher Discriminant 34

35 B reconstruction m ES = E 2 2 CM + r p i r p B 2 E 2 i p 2 B ΔE = E * B E 2 CM m ES ΔE Signal MC Events/3MeV/c 2 σ mes = 2.7MeV/c 2 m ES, GeV/c 2 Events/1MeV ΔE, GeV σ ΔE = 16.7MeV Off-resonance Data 35

36 B ± p K ± Signal Event Yield ΔE m ES 5.276<m ES <5.286GeV ΔE <29MeV Event estimate in the signal region for 1D fits to data: ΔE fit: 566±29 events && m ES fit: 588±32 events Expected Charmonium contribution: ~229±33 36