1. A recoil detector to measure hard exclusive reaction at HERMES experiment Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006 Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006 Lecture Week on The Physics of Hadrons and Ultrarelativistic Heavy Ion Collisions Lecture Week on The Physics of Hadrons and Ultrarelativistic Heavy Ion Collisions

2. Outline Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006 Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006 Motivation –DESY & HERA –Spin of the Nucleon DVCS & BH HERMES –End of polarized gaz Target –Hermes Recoil Detector Design Requirement Recoil Detector –Silicon Strip Detector (SSD) –Scintillating Fiber Tracker (SFT) –Photon Detector (PD) SFT Performance

3. DESY @ Hamburg - Germany Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006 Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006

4. HERA @ DESY Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006 Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006

5. Spin of the Nucleon Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006 Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006 Naïve parton model BUT 1989 EMC measured  = 0.120 0.094 0.138 ± ± Spin Puzzle Unpolarised structure fct. Gluons are important ! Sea quarks  q s GGGG Full description of J q and J g needs orbital angular momentum

6. The hunt for L Study of hard exclusive processes leads to a new class of PDFs q q Generalized Parton Distributions exclusive: all products of the reaction are detected missing energy (  E) and missing Mass (M x ) = 0 missing energy (  E) and missing Mass (M x ) = 0 Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006 Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006 possible access to orbital angular momentum from DIS: HERMES ~0.3

7. isolate BH-DVCS interference term non-zero azimuthal asymmetries DVCS Bethe-Heitler (BH) HERMES kinematics: BH c.s. >> DVCS c.s. DVCS & BH p +  two experimentally undistinguishable processes: Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006 Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006

8. Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006 Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006 HERMES The Missing mass resolution of the Hermes is not sufficient to identify exclusive events individually and separate to them

9. End of Polarized targets at HERMES DVCS exclusivity by missing mass M x Improve Exclusivity Detect recoiling proton modify target region Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006 Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006 Detector to measure recoiling proton

10. detection of the recoiling proton detection of the recoiling proton P: 135 – 1500 MeV/c 76%  acceptance  /p PID via dE/dx background suppression background suppression semi-incl.: 5 %  associated: 11%  improved t-resolution improved t-resolution study kinematical dependences data taking 2006/2007 data taking 2006/2007 HERMES Recoil Detector Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006 Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006 Build by DESY, Erlangen, Ferrara, Frascati, Gent, Gießen and Glasgow

11. Silicon Strip Detector (SSD) Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006 Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006

12. Scintillating Fiber Tracker (SFT) Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006 Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006  p-measurement 300-1500 MeV/c  π/p PID from dE/dx for p<700 MeV/c  2 cylinders of 2x2 layers, 10° stereo angle  1mm Kuraray fibers, mirrored ends and double cladding  PMT Hamamatsu H7546B  5120 channels total  full Ф coverage Remove edge fibers 42 (36) inner (outer) modules 1318 (1320) fibers in inner parallel (stereo) sub-barrel 2198 (2180) fibers in outer parallel (stereo) sub-barrel

13. Scintillating Fiber Tracker (SFT)  Space point reconstruction  Parallel & stereo configuration  High detection efficiency  Double fiber layer per sub-barrel  MIP signal separated from noise  Spacial resolution σ  V  Multiple scattering limits resolution 1mm fiber sufficient Minimise suport structure Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006 Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006

14. Photon Detector Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006 Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006  Detect f ´s from ∆ resonnance  Reconstruction if both decay f ´s detected  Contribute to the pion/proton PID separation (together with SFT) for p> 600 MeV/c  MIP signal are far away from pedestal  multilayer construction with parallel and stereo strips  Cosmic trigger generator

15. Photon Detector Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006 Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006  6 layer (inside out)  6mm Tungsten  A layer: 60 strips along z axis  3mm Tungsten  B layer: 44 strips -45° stereo angle  3mm Tungsten  C layer: 44 strips +45° stereo angle  2 WLS on both side of each strips  radius 20cm  dimensions of strips 2cm x 1.1cm x 28cm

16. Recoil Detector - installation Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006 Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006

17. SFT Current Status Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006 Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006 Clear hit in SFT with low background of course subject to optimization but nevertheless the SFT detector worked from the beginning as expected

18. Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006 Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006 SFT Callibration  Callibration data (blue LED pulser) from Gießen test was re-fitted with Poisson & Gauß fit  Gain (extracted from fit) vs. high voltage

19. Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006 Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006 SFT Origins of Crosstalk

20. Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006 Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006 SFT Crosstalk Correction  Tracklet Algorithm: combine signal in adjacent fibers into one cluster.  Cluster Algorithm: search for the hightest signal, then add the signal of the PMT channels left, right, up and down.

21. SFT Crosstalk & Clustering Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006 Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006

22. SFT perfect agreement between MC and data Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006 Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006  Digitization carfully improved  reasonable energy reponse of the SFT  MC and cosmics data agree perfectly

23. Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006 Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006 SFT Gain Correction & TDC cut

24. Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006 Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006 More positive

25. Summary and Outlook Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006 Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006 Silicon –Hardware not yet in perfect shape –Some more time needed –Need to understand data Scintillating Fiber Tracker –Fine calibration –Crosstalk correction and Clustring –π/p PID from dE/dx Photon Detector –Comparision with MC for energy deposition need more investigation –Crosstalk in PMT END

26. Extra

32. SFT Crosstalk Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006 Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006 h 1,2,3,4 h = = + h 2 h 3 h 4 h 1 + + h + + h 2 h 3 h 4 h 1 + + h + h + h 2 h 3 h 4 h 1 + +

33. Extra

40. Design Requirement Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006 Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006

41. SSD Current Status Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006 Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006 SFT only track Prediction for Hits in SSD SFT integrates over several bunches TDC cut Each hit used in track needs to have one correct timestamp Good tool for alignment P and N side different gain. Signal on N side cut off Hardward not yet in perfect shape.

42. Photon Detector Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006 Roberto Francisco Perez Benito Hyytiälä, 25 -30 September 2006 Require exactly 1 lepton in Spectrometer with cut on momentum (and coplanarity) Require lepton momentum in [25.5-27.6552](GeV/c) In addition proton momentum > 1.2 GeV/c Fine calibration