1. P.F.Ermolov SVD-2 status and experimental program VHMP 16 April 2005 SVD-2 status and experimental program 1.SVD history 2.SVD-2 setup 3.Experiment characteristics as from April’2002 run 4.Current status and physics program P.F.Ermolov SINP MSU Moscow Talk at VHMP 2005, Dubna, Russia 16-17 April 2004

2. P.F.Ermolov SVD-2 status and experimental program VHMP 16 April 2005 SVD-1 experiment Spectrometer with a Vertex Detector (SVD) on a proton beam channel #22 of Protvino 70 Gev accelerator went through few stages of development. SVD-1 used a fast cycling bubble chamber as a vertex detector and a magnetic spectrometer with MWPC With this setup, an estimate of near-threshold charm creation cross-section was obtained as

3. P.F.Ermolov SVD-2 status and experimental program VHMP 16 April 2005 SVD-1  SVD-2 To increase the rate of event collection, a bubble chamber was replaced by the MicroStrip Vertex Detector (MSVD) with 10,000 amplitude channels To register neutral particles: 1,500-channels  - detector Particle identification: wide-aperture threshold Cerenkov detector

4. P.F.Ermolov SVD-2 status and experimental program VHMP 16 April 2005 SVD-2 detector layout

5. P.F.Ermolov SVD-2 status and experimental program VHMP 16 April 2005 SVD-2 tracking detector (cf. Karmanov’s talk) Si active target 1 mm strip pitch 4 mm inter-plane spacing PbC Tracking detectors 25 μm 50 μm X Y U W X Y 10 mm Z from primary vertex reconstruction

6. P.F.Ermolov SVD-2 status and experimental program VHMP 16 April 2005 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

7. P.F.Ermolov SVD-2 status and experimental program VHMP 16 April 2005 SVD-2 run I (April '2002) Intensity 500-600×10 3 protons/cycle (1.2 sec) Total target thickness ~0.5% of hadronic length 400-600 events/cycle registered 53,000,000 events stored Integral luminosity L=1.6 nb -1 3 target materials: Si, C and Pb

8. P.F.Ermolov SVD-2 status and experimental program VHMP 16 April 2005 Experimental accuracies - geometry X,Y-resolutions for tracks fitted: –From MSVD 8-10  m –Secondary tracks from spectrometer700  m Z-resolution: –for the primary vertex: 70-140  m –for the secondary vertex from MSVD: 200-300  m Impact parameter resolution: ~ 14  m

9. P.F.Ermolov SVD-2 status and experimental program VHMP 16 April 2005 Experimental accuracies Momentum resolution for the 5 GeV tracks: 1% Effective mass resolution: –K 0 : 4.4 MeV –  : 1.6 MeV –  0 :12 MeV Cerenkov detector efficiency : 70% for the pions in 3-20 GeV momentum region

10. P.F.Ermolov SVD-2 status and experimental program VHMP 16 April 2005 SVD-2M 2003-2005 developments: 1.Liquid hydrogen target 2.A new vertex detector with a higher efficiency and a lower multiple scattering. New construction for replacing elements when needed 3.Much better tracking in a forward part of spectrometer due to 9 double planes of straw tubes with a 200  m resolution 4.Increased intensity capabilities of proportional chambers by installing beam killers

11. P.F.Ermolov SVD-2 status and experimental program VHMP 16 April 2005 SVD-2M (cont.) 5.New fast electronics for gamma-detector readout 6.Efficiency of Cerenkov detector increased to 85-90% 7.2 different triggers on the high multiplicity events are being created All these jobs are close to be finished soon and we hope for the successful tests during our end of 2005 run

12. P.F.Ermolov SVD-2 status and experimental program VHMP 16 April 2005 Plans for 2005-2007 With a new setup we plan to make physics in 3 directions: High multiplicities in hadron collisions with hydrogen target (first priority) Near-threshold charm creation (Si, C, Pb targets) Searches for new hadron states (both types of targets) The program is planned for years 2005-2007 with obtaining a total luminosity of ~ 50 nb -1.

13. P.F.Ermolov SVD-2 status and experimental program VHMP 16 April 2005 On results of the physics analysis It will be discussed in more details in V.Popov talk. I would like to make a few comments. 1.High multiplicities. At this picture,an event with 27 tracks in the vertex detector is presented.

14. P.F.Ermolov SVD-2 status and experimental program VHMP 16 April 2005 On results of the physics analysis (cont.) At this picture, the multiplicity distribution for the proton- carbon interactions is presented. Some slope changes could be seen near the 30 tracks point.

15. P.F.Ermolov SVD-2 status and experimental program VHMP 16 April 2005 On results of the physics analysis (cont.) But Monte-Carlo simulations in Amelin model showed that there is a contribution to the multiplicity by the events with the secondary interactions in the same nucleus. So, for the detailed investigations we need to use a pure hydrogen target.

16. P.F.Ermolov SVD-2 status and experimental program VHMP 16 April 2005 On results of the physics analysis (cont.) 2. The main goal of the April’2002 run was to collect data on the charm creation cross sections near the threshold. An analysis proved to be rather complicated, and we hope to obtain a few hundred of events with D-mesons by the end of the year. We have already some events, and the little statistics is due to very rigid selection used by now.

17. P.F.Ermolov SVD-2 status and experimental program VHMP 16 April 2005 On results of the physics analysis (cont.) As an illustration, here is an invariant mass distribution for K+  - system with both tracks having large impact parameters in both x,y planes and its (secondary) vertex is within 3 mm from a primary one. Further analysis is going on.

18. P.F.Ermolov SVD-2 status and experimental program VHMP 16 April 2005 On results of the physics analysis (cont.) 3.Remarks on the pentaquark search. In 2004, SVD collaboration published the results on the search of the narrow resonance in K 0 s p system. At the level of 5.5 , we found a resonance with a  <25 MeV and a cross-section of 30-120  b.

19. P.F.Ermolov SVD-2 status and experimental program VHMP 16 April 2005 On results of the physics analysis (cont.) At this picture, a result of a resonance search made in the beginning of 2004 is presented. Main criteria were: –Number of charged tracks in vertex detector  5 –K0 registered if its decay length is  34 mm (average ~20 mm) With this criteria, ~ 5,000 events were selected and analyzed

20. P.F.Ermolov SVD-2 status and experimental program VHMP 16 April 2005 New pentaquark analyzes (2004-2005) In the first one, the same K 0 decay region was used with another reconstruction method but without any selection criteria and without using Cerenkov detector information This resulted in a much higher number of K 0 to be analyzed The second one: K 0 decaying after the vertex detector (5-70 cm) were selected, using only spectrometer information to reconstruct tracks (“distant” K 0 ) Possibly much higher number of K 0 to be included into analysis As a result, the total number of K 0 was increased by more than an order of magnitude

21. P.F.Ermolov SVD-2 status and experimental program VHMP 16 April 2005 New pentaquark analyzes (cont.)

22. P.F.Ermolov SVD-2 status and experimental program VHMP 16 April 2005 New pentaquark analyzes (2004-2005) At pictures, well pronounced peaks with a significance of about 6  each can be seen in the mass region of 1522-1524 MeV. They are from two different samples, with a 300 events over background in total. Samples are not intersecting and are from the different kinematical regions. It doesn’t look at all as a statistical fluctuation.

23. P.F.Ermolov SVD-2 status and experimental program VHMP 16 April 2005 New pentaquark analyzes (2004-2005) We plan to make new cross-checks of our analysis, to study momentum and angular characteristics of this resonance and try to make conclusions on its creation mechanism