1. A.Kubarovsky, V.Popov. Recent results from SVD-2 experiment QFTHEP 17 June 2004 Recent results from SVD-2 experiment 1.Current status 2.Pentaquark search 3.Charmed mesons A.Kubarovsky, V.Popov SINP MSU Moscow (for SVD collaboration) Talk at QFTHEP 2004, Peterhof, St.Petersburg, Russia 17-23 May 2004

2. A.Kubarovsky, V.Popov. Recent results from SVD-2 experiment QFTHEP 17 June 2004 SVD-2 experiment The main goals (when started in 2000): –Cross section of charm creation at near-threshold energies –A-dependencies –Searches for intrinsic charm of nucleons (Brodsky,...) Most of statistics was collected in 2002 Pentaquark analysis since ‘2003 fall

3. A.Kubarovsky, V.Popov. Recent results from SVD-2 experiment QFTHEP 17 June 2004 SVD-2 detector layout

4. A.Kubarovsky, V.Popov. Recent results from SVD-2 experiment QFTHEP 17 June 2004 SVD-2 tracking detector Si active target 1 mm pitch PbC Tracking detectors 25 μm 50 μm X Y U W X Y 10 mm

5. A.Kubarovsky, V.Popov. Recent results from SVD-2 experiment QFTHEP 17 June 2004 SVD-2 trigger Level I Based on energy depositions in 5  8 Si active target strips Basic principle is to look for the >2...3 MIPs depositions in consecutive planes Decision time: 220 ns "Non-usable" events contamination: < 10% Level II Not implemented yet... Basic idea - a search of "secondary" activity A simplified "fast" information from vertex tracking detector to be used

6. A.Kubarovsky, V.Popov. Recent results from SVD-2 experiment QFTHEP 17 June 2004 SVD-2 run I (April '2002) IHEP Protvino U-70 accelerator Proton beam 70 GeV/c Intensity 5-6×10 5 1/cycle (1.2 sec) Total target thickness ~0.5% of hadronic length 400…600 events/cycle registered 53,000,000 events stored

7. A.Kubarovsky, V.Popov. Recent results from SVD-2 experiment QFTHEP 17 June 2004 Experimental accuracies X,Y-resolutions for tracks fitted: 8…10  m Z-resolution: –for the primary vertex: 70… 130  m –for the secondary vertex: 200… 300  m Impact parameter resolution: ~ 14  m Momentum resolution for the 5 GeV tracks: 1% Effective mass resolution: –K0: 4.4 MeV –  : 1.6 MeV

8. A.Kubarovsky, V.Popov. Recent results from SVD-2 experiment QFTHEP 17 June 2004 Primary vertex Z-coordinate in SVD-2 active target SVD-2 data analysis Si Pb Si C Si – 300  m; Pb – 220  m; С – 500  m  z = 70÷130µm,  x,y = 7÷10µm

9. A.Kubarovsky, V.Popov. Recent results from SVD-2 experiment QFTHEP 17 June 2004 K 0 s and Λ 0 effective masses K 0 s M = 497.61 ± 0.09 (stat.), σ=4.4 MeV/c 2 Λ 0 M = 1115.32 ± 0.05 (stat.), σ=1.6 MeV/c 2

10. A.Kubarovsky, V.Popov. Recent results from SVD-2 experiment QFTHEP 17 June 2004 u u d +2/3 − 1/3 p K−K− s u − 2/3 Meson: quark-antiquark ++ u u d d s + 1/3 − 1/3 +2/3 − 1/3 +2/3 Pentaquark: 4 quarks + 1 antiquark Exotic if antiquark is of the different flavour Baryon: three quarks Hadron nicknames

11. A.Kubarovsky, V.Popov. Recent results from SVD-2 experiment QFTHEP 17 June 2004 A start of pentaquark history  An idea of five-quark states was discussed since late 60’s (Jaffe, Lipkin, Strotteman, …)  First estimates in the Skyrme model (Chemtob, Praszalowicz, Walliser) – 1985...  There were no conclusive results from experimental searches “The general prejudice against baryons not made of three quarks and the lack of any experimental activity in this area make it likely that it will be another 15 years before the issue is decided”. (PDG, 1986)

12. A.Kubarovsky, V.Popov. Recent results from SVD-2 experiment QFTHEP 17 June 2004 PDG – in “Particle listings under revision”

13. A.Kubarovsky, V.Popov. Recent results from SVD-2 experiment QFTHEP 17 June 2004 In the ‘2003 fall... uudds quark content Predicted by Diakonov,Petrov and Polyakov Z.Phys A 359, 305(1997) Supposed to be of 1530 MeV/c 2 mass, width <15 MeV/c 2 and to decay into nK + or pK 0 Observed by several experiments (LEPS,DIANA,CLAS,…) in both decay modes The pK 0 mode can be searched for by SVD-2: good resolution for K 0 s and proton identification

14. A.Kubarovsky, V.Popov. Recent results from SVD-2 experiment QFTHEP 17 June 2004 Anti-decuplet of q4q-bar states DPP model modified (DP hep-ph/0310212) (1530)  < 15 MeV M=1760-1810 M=1650-1690 M=1862 = 5   +

15. A.Kubarovsky, V.Popov. Recent results from SVD-2 experiment QFTHEP 17 June 2004 Data sample ~35,000 events sample for D-meson searches was used Primary selection mainly based on the presence of well-defined secondary vertices in the close- to-target region Secondary tracks are measured by vertex detector Allowed decay length is 1…35 mm (av. 20 mm), means that only ~10% of K 0 s to be reconstructed

16. A.Kubarovsky, V.Popov. Recent results from SVD-2 experiment QFTHEP 17 June 2004 Events selection for pentaquark analysis ≤ 5 charged tracks from primary vertex to reduce combinatorial background K 0 s selection: –2 oppositely charged tracks from secondary vertex –490 ≤ M ππ ≤ 505 MeV/c 2 –M pπ ≥ 1120 MeV/c 2 (→ not Λ 0 ) Proton selection: –Positive track from primary vertex –Momentum of 4…21 GeV/c –Absence of a Cerenkov detector hit

17. A.Kubarovsky, V.Popov. Recent results from SVD-2 experiment QFTHEP 17 June 2004 pK 0 s spectrum analysis Cut applied: pK 0 s system goes forward in center-of-mass system Narrow peak at 1526 MeV/c 2 is observed FRITIOF simulated background fails to reproduce the real shape Peaks in higher mass region can be attribu- ted to Σ* + bumps

18. A.Kubarovsky, V.Popov. Recent results from SVD-2 experiment QFTHEP 17 June 2004 Cut applied: P p >P K0 to eliminate bumps (cf. B.Levchenko, arXiv:hep-ph/0401122) Background can be described in different ways: –FRITIOF simulations –Plain polynom fitting –Random-star (not shown) All three give the shape compatible to the experimental one

19. A.Kubarovsky, V.Popov. Recent results from SVD-2 experiment QFTHEP 17 June 2004 Pentaquark parameters at SVD-2 Number of events within a peak: 50 over background of 78, gives a significance of 5.6 σ Mass: 1526 ± 3(stat.) ± 3(syst.) MeV/c 2 Width Γ < 24 MeV/c 2 (below experimental resolution) Strangeness could not be defined directly, but there are no reported S= -1 states in this mass region

20. A.Kubarovsky, V.Popov. Recent results from SVD-2 experiment QFTHEP 17 June 2004 Cross section and A-dependence We estimate the total cross-section of pA→Θ + + X as 30÷120 μb/nucleon We fail to find the difference in A-dependence of Θ + events from that of total for inelastic events (~A 0.7 ) The ratio of Θ+ peak events to the total of K 0 events for different target materials

21. A.Kubarovsky, V.Popov. Recent results from SVD-2 experiment QFTHEP 17 June 2004 Theta mass with another set of cuts applied Peak width: 24 18 MeV/c 2

22. A.Kubarovsky, V.Popov. Recent results from SVD-2 experiment QFTHEP 17 June 2004 Experiments zoo Spring8 ELSA JLab-p HERMES ITEP pp   +  +. COSY-TOF DIANA SVD-2 JLab-d ZEUS CERN/NA49 H1

23. A.Kubarovsky, V.Popov. Recent results from SVD-2 experiment QFTHEP 17 June 2004 Pentaquark observations A table from E.Klempt, hep-ph/0404270

24. A.Kubarovsky, V.Popov. Recent results from SVD-2 experiment QFTHEP 17 June 2004 Theta masses from different experiments Certain mass shift can be observed between the K + n and K 0 p modes Spring-8 CLAS-d CLAS-p SAPHIR ITEP HERMES COSY ZEUS SVD-2 15201540 1560 K0pK0p K+nK+n

25. A.Kubarovsky, V.Popov. Recent results from SVD-2 experiment QFTHEP 17 June 2004 H1: charmed pentaquark? M = 3099 ± 3 ± 5 MeV Minimal quark content: uuddc To be confirmed!

26. A.Kubarovsky, V.Popov. Recent results from SVD-2 experiment QFTHEP 17 June 2004 Exclusive reaction searches LEPS γn  K + K - n CLAS γd  K + K - pn

27. A.Kubarovsky, V.Popov. Recent results from SVD-2 experiment QFTHEP 17 June 2004 Near-threshold D 0 production Search for the D 0  K + π - decays Different reconstruction methods used (not cross-checked yet…) 24 events over background of 12 V.Volkov 15/06/04

28. A.Kubarovsky, V.Popov. Recent results from SVD-2 experiment QFTHEP 17 June 2004 Current status New analysis software is able to process “distant” V 0 s : –K 0 - 10 times more statistics (for Θ + analysis and charm searches) –Λ – up to 100 times more statistics, allowing Ξ - decays reconstruction to search for Ξ 3/2 pentaquark claimed by NA49 Better kinematical fitting for secondaries to improve effective mass resolution