1. 1 M. Güler (METU, Ankara) Collaboration Associated Charm Production in neutrino interactions HEP2007 July 19-25, 2007 Manchester, England Belgium (Brussels, Louvain-la-Neuve), CERN, Germany (Berlin, Münster), Israel (Haifa), Italy (Bari, Cagliari, Ferrara, Naples, Rome, Salerno), Japan (Toho, Kinki, Aichi, Kobe, Nagoya, Osaka, Utsunomiya),Korea (Gyeongsang), The Netherlands (Amsterdam), Russia (Moscow), Turkey (Adana, Ankara) for

2. 2 W g  D+D+X – c c – Gluon bremsstrahlung Associated Charm production Associated Charm production In  CC interactions In the past, Measurement of prompt tri-muon events        and same-sign di- muons –Large background from  and K decays –Observed rate much larger than expected from theoretical calculations. (Nucl.Phys.B 173 (1980), 487) Recently, A search done in CHORUS –1 event observed with the characteristics of associated charm production (Phys. Lett B 539 (2002),188) (Phys. Lett B 539 (2002),188)

3. 3 Associated Charm production In  NC interactions Gluon bremsstrahlung & Z-gluon fusion In the past, Only one event observed by E531 -Production rate Indirect search performed by NuTeV A.Alton et al., Phys. Rev. D64 (2001) 539 –Production rate (normalised to CC at 154 GeV) – Z g D+D+X – c c c g Z D+D+X – c

4. 4 The beam  Wide Band Beam –4-years of operation (1994-1997) –5.06  10 19 POTs – ~ 27 GeV West Area Neutrino Facility at CERN SPS   e  e ~ 

5. 5 CHORUS detector detectorCHORUS Calorimeter Air core spectrometer and emulsion tracker Air core spectrometer and emulsion tracker Veto plane Muon spectrometer Muon spectrometer  - -  - - h-h- h-h- T=5°C Nucl. Instr. Meth A 401 (1997),7 Events are classified as 0  sample 1  sample based on electronic detector information

6. 6 Automatic Scanning track 90  m plastic backing 350  m (175  m) emulsion sheet CCD camera CCD camera microscope stroke tomographic image X50 magnification ~3  m focal depth 150x150  m view Tracks reconstructed by a hardware video processor frame to frame emulsion grains coincidence 350  m (175  m) emulsion sheet emulsion plate T.Nakano, Ph.D. Thesis, Nagoya Univ., 1997

7. 7 Offline Emulsion Analysis Track segments from 8 plates overlapped At least 2-segment connected tracks Eliminate passing through tracks Reconstruct full vertex topology 1 2 1 2 3 Location of interaction vertex guided by electronic detector. Full data taking around interaction vertex called NETSCAN Offline tracking and vertex reconstruction 3

8. 8 Decay Search Reconstructed primary vertexReconstructed primary vertex Isolated track having impactIsolated track having impact parameter between IP min < ip< Ip maxIP min < ip< Ip max Ip min = sqrt(5.0 2 +(2*dx*  ) 2 ); Ip max <130  m  = sqrt(0.003 2 +(0.0194*  ) 2 ) Track at least two plate long connected and matched with detector track Track quality  2 <1 Readout of all tracks (  <0.4 rad ) at the surface of each plates around a primary interaction Reconstruct vertex based on minimum distance search Offline selection: Principle 8-plates 1.5 mm

9. 9 Manual Scanning results C1 ~23% V2 ~41% C3 ~24% V4 ~11% V6 ~0.1% Low momentum ~19% Passing through ~23% h ± secondary ~33% h 0 secondary ~7%  conversion ~12% Overlay interactions 7% Decay topologyBackground topology selection Purity : 68 %

10. 10 Associated Charm production Associated Charm production 3(3) events satisfy the topological selection in NC (CC) interactions Kinematical Selection: p t > 250MeV/c applied to C1 topology (significantly reduced ‘white Kink background’ ) φ> 10 mrad applied to V2 topology (in order to eliminate 2-body decays of neutral strange particles ) Four events satisfy the above selection criteria 0  sample 1  sample

11. 11 Ev-ID: 8133 12312(NC) E=29.9GeV P d4 >2.72 GeV/c @ 90 CL. P d2 >4.66 GeV/C @ 90 CL. P d1 >1.39 GeV/C @ 90 CL. P d3 >3.33 GeV/c @ 90 CL.  = 96 mrad fl= 63  m  = 24 mrad M min = 0.76 GeV@90% CL.  = 203 mrad fl= 977  m  =36 mrad M min = 0.96 GeV@90 CL. V2(1) V2(2)

12. 12 CCbar candidate in NC beam  int.  V2 (Event-ID: 8132 12312) (Event-ID: 8132 12312) V2 daughter Primary particle V2 daughter

13. 13 P d2 >4.11 GeV/c @ 90% C.L. P d1 >3.81 GeV/c @ 90% C.L. P d >1.82 GeV/c @ 90% C.L. Ev-Id: 7692 5575(NC) E=41.4GeV  = 104 mrad fl= 224  m  = 15 mrad M min = 0.68 GeV @ 90 CL. V2 fl= 163.0  m  = 179.0 mrad P T >0.323 GeV/c @ 90 C.L.C1

14. 14 E=40.3 GeV Ev-Id 7739 3952(NC) C3 fl= 426  m V4 fl= 884  m

15. 15 Ev-Id 7904 4944(CC) E=36.9 GeV P=-16.9 GeV/c V2  op = 340 mrad fl= 58  m  =13 mrad M min = 0.79 GeV/c @90 CL. V4 fl= 761  m

16. 16 CCbar candidate in CC beam  int. V2 daughter V4 vertex V2 vertex  (Event-ID: 7739 3952)

17. 17 MC Simulation Herwig 6.5 JHEP 0101, 010, (2001) Effiencies and background were evaluated with a simulation of detector based on GEANT3 CCNC

18. 18 MC Simulation In order evaluate Netscan efficiencies, realistic track density should be reproduced This was achieved by merging the emulsion data of the simulated events with real Netscan data. The combined data are passed through the same Netscan reconstruction and selection programs 8.5±0.3%12.3±0.5% CC events NC events Mix DATA and MC Process recontruction & selection programs

19. 19 Background Estimation A single charm event with a primary non-charmed hadron which undergoes either a decay or an interaction. There are negligible contributions from decays of other non-charmed hadrons like kaons and pions due to longer decay lengths and P t > 250 MeV/c cut Decays of neutral strange particles do not give sizeable contribution owing to coplanarity cut Background NC sampleCC sample

20. 20 Results Where, N obs is the number of candidate events N bgr = 0.18 ± 0.005 is the total background R NC/CC = 0.274 ± 0.005 is the ratio between deep-inelastic  NC and CC interactions N CC = 101,329 is the number of CC interactions  net  = 0.128  ± 0.006 is the average detection efficiency for the  NC cc sample r loc = 0.211 ± 0.004 is the ratio of the reconstruction and location efficiency of events with cc in  NC events to that of all   CC events The value obtained for this ratio at 27 GeV average neutrino energy is Result is consistent with the E531 and NuTeV measurements

21. 21 Results With the observation of one double charm event in CC interactions we obtain For the relative rate an upper limit at 90 % C.L. of Since the topology of the single candidate event is not one of the most likely Background channels. Based on the single event, the production cross-section relative to CC interactions is measured to be CC 