12 th Flavor Physics & CP Violation May 26 th -30 th , 2014

1. The NA62 experiment at CERN: status and perspectivesR. FantechiCERN and INFN – Sezionedi Pisaon behalf of the NA62 CollaborationBirmingham, Boston, Bratislava, Bristol, Bucharest, CERN, Dubna, Fairfax, Ferrara, Florence, Frascati, Glasgow, IHEP, INR, Liverpool, Louvain, Mainz, Merced, Naples, Perugia, Pisa, Prague, Rome I, Rome II, San Luis Potosi, SLAC, Sofia, Turin 12thFlavorPhysics & CP Violation May 26th-30th, 2014

2. Outline • K+®p+nntheory (short reminder) • NA62 detector layout • Strategy for the measurement • Perspectives for 2014 and beyond • Conclusions R. Fantechi - 12th Flavor Physics & CP Violation - May, 30th, 2014

3. K+ ® p+nn: clean theoretical environment FCNC loop processes: s->d coupling Highest CKM suppression • SD contribution dominates • top quark contribution computed at NLO QCD and 2-loop EW corrections • c quark loop contribution computed at NNLO QCD and NLO EW corrections • correctionfor LD contributions • Hadronic matrix element related to the precisely measured BR (K+®p0e+n) • Branching ratio proportional to |Vts *Vtd|2 K ® pnnare the most sensitive probes to NP models among B and K decays The combinedmeasurementofK+ and KLmodescouldshed light on the flavourstructureof NP (DS=2 / DS=1 correlation) SM predictions [Brod, Gorbahn, Stamou, Phys. Rev D83,034030 (2011)] BR(K0) = (2.43±0.39±0.06)*10-11 BR(K+) = (7.81±0.75±0.29)*10-11 First error CKM parametric, dominated by Vcb Second error theoretical, mostly LD corrections R. Fantechi - 12th Flavor Physics & CP Violation - May, 30th, 2014

4. K ® pnnNP sensitivity General model with new flavour structure: Z’ gauge boson mediating FCNC at tree level [A. Buras, F. De Fazio, J. Girrbach, JHEP 1302 (2013) 116] K sensitive to mass scales beyond those explored from LHC (MZ’ > 5 TeV/c2) More specific NP models Littlest Higgs with T-parity, Acta Phys. Polonica B41(2010)657 Custodial Randall-Sundrum JHEP 0903 (2009) 108 • Started to be probed at LHC, small effects in B physics. • Best probe of MSSM non-MFV[JHEP 0608 (2006) 064] • E.g. non-MFV in up-squarkstrilinearterms • Stillnotexcludedby the recentLHCb data. R. Fantechi - 12th Flavor Physics & CP Violation - May, 30th, 2014

5. Today status of K ® pnn E787/E949 @Brookhaven: 7 candidates K+ ® p+nn 2 experiments, stopped kaon technique SeparatedK+beam(710 MeV/c, 1.6MHz) PID: range (entireπ+→μ+→e+decaychain) Hermeticphoton veto system Probability of all events to be background ~ 10-3 Expected background: 2.6 events Phys. Rev. D77,052003 (2008), Phys. Rev. D79,092004 (2009) E391a @ KEK: Phys. Rev. D81,072004 (2010) Future experiments: KOTO@JPARC (KL® p0nn), ORKA@FNAL (K+® p+nn) First results during summer cancelled R. Fantechi - 12th Flavor Physics & CP Violation - May, 30th, 2014

6. NA62 goals • Collection of O(100) K+ ® p+nnevents in two years of running • 10 % measurement of the branching ratio • This requires at least 1013Kaon decays • 75 GeV beam helps in background rejection • Event selection with Pp<35 GeV/c • i.e. Kp2 decays have around 40 GeV of electromagnetic energy • O(1012) rejection factor of common K decays • Main contribution from Km2 (63%) and Kp2 (21%) • Kinematics resolution • Efficient veto detectors • Particle ID • Precise timing • Expected acceptance O (10%) R. Fantechi - 12th Flavor Physics & CP Violation - May, 30th, 2014

7. NA62 high-intensitykaonbeam • SPS primaryprotonbeam @ 400 GeV/c • Protons on target: 3 x 1012 / pulse • Duty cycle ~ 0.3 • Simultaneous delivery to LHC • Secondarycharged beam 75 GeV/c • To optimize kaon production • Momentum bite 1% • Angular spread in X and Y < 100 mrad KTAG • Size @ beam tracker: 5.5 x 2.2 cm2 • Rate @ beam tracker: 750 MHz • 6% K+ (others: 70% p+, 24%proton) • Rate downstream 10 MHz (mainlyK+decay) • K decayrates: 4.5 x 1012 /year • In a 60 m decay volume R. Fantechi - 12th Flavor Physics & CP Violation - May, 30th, 2014

8. The NA62 detector Dipole magnet 4 straw-tracker stations g veto g veto SPECTROMETER p/m ID 17m, 1 atm Ne IRC SAC Differential Cherenkov for K+ ID in beam KTAG Charged veto RICH KTAG CHANTI CHOD Target Beam tracker Si pixels, 3 stations Beam Pipe GTK Large angle photon vetoes OPAL lead glass 11 stations in vacuum, 1 in air Forward g veto NA48 LKr calorimeter Muon veto Fe/Scint MUV 8 LKr LAV R. Fantechi - 12th Flavor Physics & CP Violation - May, 30th, 2014

9. The measurement • Signature: one incident kaon, 1 charged output track • Missing mass distributions: m2miss = (PK-P track(hypp+))2 • Define two regions to accept candidate events • Backgrounds • K+ decay modes • Accidental signal track matched with a K-like one Photon and muon vetoes + particle ID to fight the background R. Fantechi - 12th Flavor Physics & CP Violation - May, 30th, 2014

10. Guiding principles for the detectors • Good tracking devices • Accurate measurement of the kaon momentum • Accurate measurement of the pion momentum • Missing mass cut: O(105) rejection factor on Km2, O(104) on Kp2 • Veto detectors • For photons to reduce the background by a factor 108 • For muons add a rejection factor of O(105) • Particle identification • Identify kaons in the beam • Identify positrons • Additional p/m rejection [O(102)] • Precise timing • To associate in time the kaon with the decay products R. Fantechi - 12th Flavor Physics & CP Violation - May, 30th, 2014

11. Reconstruction of the beam kaon • Time : Gigatracker, KTAG • Track reconstruction: Gigatracker • Gigatracker: • 3 Si pixel station (300*300 mm2 pixels) with readout chips bonded • X/X0 < 0.5%/station • Capability to handle 750 MHz beam rate • Installed inside an achromat • From test beam and simulation • s(t) ~ 200 ps/station • s(PK)/PK = 0.2% • s(dX,Y/dZ)K = 15 mrad Chip under test at CERN Commissioning on the beam line in September 2014 R. Fantechi - 12th Flavor Physics & CP Violation - May, 30th, 2014

12. Reconstruction of the charged pion • Time : RICH • Track reconstruction: Straw spectrometer • RICH time resolution < 100 ps • Spectrometer • 4 straw chambers in vacuum • 9.6 mm radius mylar tubes, 2.1 m long • 4 planes of staggered tubes per view, 4 views in a chamber • X/X0 0.1% per view ®2% total • Dipole magnet with 265 MeV/c PT kick • Resolution • s(P)/P = 0.32% Å 0.008 P [GeV/c] • s(dX,Y/dZ) = 20-50 mrad Construction almost finished Commissioning in September 2014 R. Fantechi - 12th Flavor Physics & CP Violation - May, 30th, 2014

13. Kaon-pion matching • Very different rate • Beam@Gigatracker: 750 MHz • decays@downstream detectors: 10 MHz • Wrong kaon-pion assignment will spoil the kinematical reconstruction • Match in time and in space • Gigatracker resolution: 200 ps/station • KTAG resolution: < 100 ps • RICH resolution: < 100 ps • Find a vertex in Gigatracker (CDA cut) • Mis-matching probability < 1%, could go down with analysis optimization R. Fantechi - 12th Flavor Physics & CP Violation - May, 30th, 2014

14. Kinematics Signal/background rejection by kinematics K+ ® p+ p0: ~5 *103 K+ ® m+ n : ~1.5 *104 Inefficiencies due to: Non gaussian tails from multiple scattering Pileup in the Gigatracker R. Fantechi - 12th Flavor Physics & CP Violation - May, 30th, 2014

15. Photon rejection • IRC, SAC, LKr, LAV • Hermetic coverage up to 50 mrad • O(108) p0 rejection from K+®p+p0 • Thanks to the cut Pp <35 Gev® Ep0 >40 Gev • If one photon is lost above 50 mrad, the other is going in the LKr • For Eg >10 GeV, LKr inefficiency measured from data is <10-5 • 10-4 inefficiency down to 100 MeV in LAV Lead glass blocks from OPAL 12 stations (11 in vacuum) Ready NA48 em calorimeter New readout electronics being commissioned Calorimeters at low angle (<1 mrad) Shashlik technology IRC being built, SAC in place LAV R. Fantechi - 12th Flavor Physics & CP Violation - May, 30th, 2014

16. Particle ID: calorimeters • p/m/e separation • NA48 LKr calorimeter • Em/hadronic/mip cluster id • Very good mip signal • MUV1&2: Fe-scintillator • Hadronic/mip cluster id • Usable also in the trigger (pion energy) • MUV3: scintillator tiles seen by two PMs • Fast muon counter, ineff. <% • Used in the L0 trigger • Global p/m separation (from simulation + test beam): 105 • MUV2 and MUV3 ready, MUV1 to be installed during the summer From technical run 2012 R. Fantechi - 12th Flavor Physics & CP Violation - May, 30th, 2014

17. Particle ID: Rich • p-m separation: RICH • 17 m long filled with Ne at 1 Atm • Array of 20 mirrors, 17m focal length • 2x 1000 PMs in the focal plane • 9 cm radius internal beam pipe • 14 GeV threshold for pions • Full length prototype tested in 2009 • Full detector under installation • p-m separation > 102 up to 35 GeV • Time resolution 80 ps • To be used also in the L0 trigger R. Fantechi - 12th Flavor Physics & CP Violation - May, 30th, 2014

18. Particle ID in the beam • K-p separation in the beam: KTAG • Differential Cherenkov counter (CEDAR, from SPS) • Filled with N2 or H2 • New external optics, PMs and readout • 50 MHz particle rate • Installed and partly commissioned in 2012 • Kaon tagging with <100 ps time resolution • Sub-percent pionmis-tagging for K efficiency > 95% • K-p time matching • Suppression of background for accidental tracks by interactions of the beam with the Gigatracker stations R. Fantechi - 12th Flavor Physics & CP Violation - May, 30th, 2014

19. Trigger and DAQ • Strong requirement: handle 10 MHz kaon decay rate and reduce it to 10 KHz bandwidth to tape • Multilevel trigger system • L0 based on digital primitives from fast detectors • FPGA based, latency ~ 1ms • A smart L0 trigger processor gathers all primitives and issue a L0 decision • Reduction factor: 10 MHz -> 1 MHz • L1 PC based • Uses data from all the detectors except LKr • Whole event analysed by a single PC • Max latency 1s • Reduction factor: 1 MHz -> 100 KHz • L2 PC based, uses all data • Performed by the same PC as L1 • Latency: spill length • Reduction factor: 100 KHz -> 10 KHz Trigger primitives construction Use fast detectors (RICH, MUV), energy in the LKr and at least in a fraction of the LAV system R. Fantechi - 12th Flavor Physics & CP Violation - May, 30th, 2014

20. NA62 Sensitivity & backgrounds R. Fantechi - 12th Flavor Physics & CP Violation - May, 30th, 2014

21. Additional NA62 K PhysicsProgram R. Fantechi - 12th Flavor Physics & CP Violation - May, 30th, 2014

22. Status of the installation R. Fantechi - 12th Flavor Physics & CP Violation - May, 30th, 2014

23. NA62 data taking plans • Complete the installation of the detector • Before the SPS restart in Autumn after LS1 • 2 months run at the end of 2014 • Complete the commissioning with particles • Lower intensity • Likely reach SM sensitivity • Nominal beam intensity in 2015, 2016, 2017 • To collect ≥100 events • Complete data taking before LS2 R. Fantechi - 12th Flavor Physics & CP Violation - May, 30th, 2014

24. Conclusions • NA62 detector construction is almost complete • The first run with beam will start on October 2014 • Commissioning with particles • Almost SM sensitivity • Data taking will continue at least up to LS2 • Beside K+®p+nn, plans for studies of many rare decay channels R. Fantechi - 12th Flavor Physics & CP Violation - May, 30th, 2014

25. Artist’s view of the installation activity… Thank you! R. Fantechi - 12th Flavor Physics & CP Violation - May, 30th, 2014

26. Spares R. Fantechi - 12th Flavor Physics & CP Violation - May, 30th, 2014

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34. Overview of TREK 0.25% precision |U|<2 10-8 for M<200 MeV SM extensions with massive gauge boson A’ Sensitivity: mixing parameter ~10-6 for 10<M(A’)<100 MeV