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Preparation for the K +  p + nn Analysis

Preparation for the K +  p + nn Analysis. Giuseppe Ruggiero (CERN) Meeting with SPSC Referees CERN, 02/04/2012. Question. Given the last LHC results on New Physics searches and on the Higgs, can the K  pnn BR measurement still be considered a “golden mode” for new physics discovery ?.

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Preparation for the K +  p + nn Analysis

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  1. Preparation for the K+p+nn Analysis Giuseppe Ruggiero (CERN) Meeting with SPSC Referees CERN, 02/04/2012 Giuseppe Ruggiero - Meeting with SPSC referees

  2. Question • Given the last LHC results on New Physics searches and on the Higgs, can the Kpnn BR measurement still be considered a “golden mode” for new physics discovery ? Gino Isidori private comunication Giuseppe Ruggiero - Meeting with SPSC referees

  3. LHC results and New Physics Scenarios ˜ b ˜ ˜ ˜ u,d,c • Experimentalresults/assumptions: • Flavourstructure in agreement with SM predictions(B-factories). • SUSY notobserveddirectly at LHC up tonow. • Higgsobserved at LHC and MH = 125 GeV/c2(assumption). • Theoreticalassumption: • New Physicshas a Supersymmetricstructure. • Theoreticalconsequences: • SUSY MFV unlike. • SUSY high tanbscenariosruled out. • Mostprobable scenario “Natural SUSY”: • heavy • not light • light (no significantconstraintfromdirect SUSY searches at LHC up tonow). ˜ t Giuseppe Ruggiero - Meeting with SPSC referees

  4. Possible Effects of New Physics ˜ ˜ ˜ ˜ ˜ t t t t t ˜ t † • Whereto look foreffectsof New Physics: • Physicsprocesses sensitive toeffects. • Reminder: the can contributeto SM level via loopsonly. • Z-loopamong the best places, complementarytodirectsearch(couplings vs masses). • Physicsprocesses: • FCNC decays (theoreticalclean): Bs mm , K  pnn. • Direct production of • FCNC processes: • Sensitivity to non-MFV structures of the A-terms (LR mixing) of the up-squarks mass matrices. • Expected effects: 20-30% max, both on Bs mm , K  pnn(highly correlated). • <10% precision of the SM BR required for both the channels (LHC on Bs?) • Direct production: • via gluino (production via gluon has too small BR and too high irreducible background from concurrent tt production). • High energy required (LHC 14 TeV ?) † Giuseppe Ruggiero - Meeting with SPSC referees

  5. Conclusions • The recent LHC results point towards a scenario where the Kpnn is one of the few places where new physics can give measurable effects (if new physics is SUSY…) • Our direct competitors: • LHCb: Bsmm at 10% precision • LHC @ 14 TeV: direct stop search. Giuseppe Ruggiero - Meeting with SPSC referees

  6. Preparation for the K+p+nn analysis • Goals: • Establishananalysis procedure for the K+p+nnbranchnigratiomeasurement in ordertobereadyfor the 2014 data taking. • Provide a detailedreviewof the physicssensitivityof the experiment. Giuseppe Ruggiero - Meeting with SPSC referees

  7. NA62 Physics overview Separated from signal by kinematic cuts Not separated by kinematic cuts Giuseppe Ruggiero - Meeting with SPSC referees

  8. Scheme of the K+p+nn Analysis • “Cut and count” analysis. • Mainfeatures: • Kinematics(GTK, StrawSpectrometer) • Veto (LAV, LKr, IRC-SAC, MUV3) • Particle-ID (RICH, LKr, MUV) GTK / CEDAR Spectrometer / RICH / etc. Beam pile-up solution UPSTREAM DOWNSTREAM K Candidate p+ Candidate • Toolsfor the analysis: • Simulationof the beamlinebased on Turtle and on Geant4. • Complete and detailedsimulationof the NA62 detectorsbased on Geant4. Kinematics EVENT Giuseppe Ruggiero - Meeting with SPSC referees

  9. Kinematic Selection • GTK reconstructionready. • Spectrometerreconstructionready • Complicate pattern recognitionbecauseof the geometryofone single chamber. • Works properlyalso in multi-trackenvironment (tested on K +p+p+p-). • >99% efficiencyfor single track. >95% for 3-track eventsreconstruction. • s(P)/P = 0.32%  0.009% x P (GeV/c); s(q) = 45  20 mrad (depending on Ptrack). • Kinematic selection: • 1 Track reconstructed in the Straw Spectrometer, 15 < Ptrack < 35 GeV/c. • CDA and Z reconstructed vertex (60 m fiducial region). • Cuts on m2miss. 1 view region 2 views region 3 views region 4 views region Giuseppe Ruggiero - Meeting with SPSC referees

  10. Kinematic Selection: Cuts on M2miss p+nn p+p0 R1 R2 m+ n p+p+p- Giuseppe Ruggiero - Meeting with SPSC referees

  11. Acceptances after Kinematic Selection Giuseppe Ruggiero - Meeting with SPSC referees

  12. Beam Pileup and GTK reconstruction • Pileupsimulation: DT=2ns, Rate=750 MHz • Averagetracks in GTK expected per event: 2.5 (1 K, 1.5 pileup) • All the possible GTK hit combinationsconsidered. • Realtracks: GTK hitsfrom the same track (Pileuptracks, Kaon tracks). • Faketracks: GTK hitsfromdifferent beam tracks. • Beforeselectioncuts: • Averagereconstructed track per event: 27 • Fractionof: Kaons3.6%, Pileup 5.3%, Fake 91% • RealTrackRecognition: • Discriminantvariable: global c2 • Trackrecognition: global c2 < 20. • After track recognition: • Averagereconstructed track per event: 2.6 • Fractionof: Kaons 38% ,Pileup 56%, Fake 6.1%. Giuseppe Ruggiero - Meeting with SPSC referees

  13. Beam Pileup and Kaon-ID DT for all the tracks CDA for all the tracks • Inputs for Kaon track identification: DT = Ttrack – Tevent, CDA. • ResultsafterKaon - ID: • Fractionof: Kaons99.4%, Pileup0.6%, Fake<0.1% Giuseppe Ruggiero - Meeting with SPSC referees

  14. Multi-Charged Particle Background • Decayanalyzed: p+p+p- • Dangerousconfiguration: • onep+ in the strawacceptance, the otherp+ and the p- in the beamhole. • Countermeasure: • the distancebetween MNP33 and chamber 4 allowsp- up to 60 GeV/c toenter in the acceptanceof the detectors downstream. • Possibleflaws: • p-decays and the m-islost • p-interactshadronically. • Startingpoint: Giuseppe Ruggiero - Meeting with SPSC referees

  15. Multi-Charged Particle Background RICH, CHOD, LAV11,12 multiplicitycuts: 5x102rejectionfactor, 20% signal loss The otherp+in the IRC : rejectionfactor2. Residualevents: p-decays and the m-goesoutside the acceptanceof the downstream detectors Solution: extensionsof the CHOD: 80x80 cm2 box ofscintillatorarraysbehind the RICH. LAV12 CHOD Residualevents: p-interacting in the detector material beforereaching the downstream spectrometers. Solution Segmentreconstruction in straws; Useof LAV 9, 10. RICH entrance window Straw 1 RICH exit window Straw 2 Giuseppe Ruggiero - Meeting with SPSC referees

  16. Photons in the Small Angle Region Evaluationof the effectof the material in the IRC and SAC acceptances on the photonrejectioninefficiency (beam pipe). Effectstudiedusingphotonsfromp+p0whichpassed the pnnkinematicselection. Giuseppe Ruggiero - Meeting with SPSC referees

  17. Photons in the Forward Region • Evaluate the effect of the material in front of the LKr on the photon rejection inefficiency (straw chambers and RICH). • Reminder: the LKr intrinsic inefficiency was evaluated on data (NA48 in 2007). • Probabilityofginteraction: 20% • Most part of the interactions are simplephotonconversions (e+e- pairsdetectedaswell in the LKr). • Probabilityofgnuclearinteraction:10-3 Multiplicitycuts in LAV9,10,11,12 and in the detectors downstream to the RICH applied. Giuseppe Ruggiero - Meeting with SPSC referees

  18. Muon Suppression with Calorimeters: Analysis p+ andm+generatedwithenergyfixed at 20 and 30 GeV. Showerwidthusedto discriminate betweenp+andm+both in MUV1 and LKr. • Rejectionfactorfrom LKr+MUV1:  50 (@ 20 GeV). • Rejectionfactorfrom MUV3:  104 • Total muonrejectionfactor: > 105 • p+efficiency: 90% (MUV1+LKr only). • Thisanalysisis just started. Giuseppe Ruggiero - Meeting with SPSC referees

  19. Conclusions (2011) • Several effects have been studied, or are under study: • Kinematic rejection • Effect of the non gaussian tails • Beam pileup • Multi-charged particle background • Use of the veto detectors • Spot and cure possible flaws of the layout • Photon veto: • Effect of the detector material on the photon detection efficiency • Muon-ID using the calorimeters. • The most important backgrounds are under control. • Signal acceptance always about 10%. Giuseppe Ruggiero - Meeting with SPSC referees

  20. Plans for 2012 • Preparationto the K+p+nnanalysiswill continue. • Betterdefinitionof the multiplcitycuts. • Effectof the material on the detection of the photons in the LAVs. Studyof the possibilitytomeasure the photon detection inefficiencyusing data (asithasbeendonefor the LKr in 2007). • Progress in the muonidentificationusing the calorimeters. • Determinationof the expectedlevelof background comingfrom: • K+ p+p0(g) • K+  p+p+p- • K+  m+n(g) • K+  p+p-e+(m+)n • Beaminduced background • Accurate evaluation and optimizationof the signalacceptance. Giuseppe Ruggiero - Meeting with SPSC referees

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