Anomalies in Kaon Physics: the NA62 program Francesca Bucci (INFN, Sezione di Firenze) on behalf of NA62 Collaboration XIIth Meeting on B Physics. Tensions in Flavour measurements: a path toward Physics beyond the SM 22-24 May 2017 Centro Congressi, Università di Napoli Federico II

Kaon Physics: a Building Block of the SM Discovery of strange particles: first observation of a quark-flavour not present in the ordinary matter [Nature 160 4077 (1947) 855] Postulation of neutral meson oscillation [Phys. Rev 97 (1955) 1387]  -  puzzle: first hint of P violation [Phys. Rev. 104 (1956) 254] Discovery of CP violation in the K0 mixing [Phys. Rev. Lett. 13 (1964) 138] 3-quark-model to describe the observed meson/baryon spectra [Phys. Lett. 8 (1964) 214] Prediction of the c-quark to explain the unexpectly low observed branching ratio of decay the KL  +- [Phys. Rev. D 2 (1970) 1285] First evidence of direct CP violation in the K0 [Phys. Lett. B 206 (1988) 169] F.Bucci

Kaon Physics: Toward the Present Era Kaon Experiments [1995-2010] NA48 (CERN), KTeV (FNAL), KLOE (LNF), CPLEAR (CERN), E865 (BNL), ISTRA+ (Protvino) Measurement of direct CP violation in the K0 (NA48@CERN, KTeV@FNAL) [Phys. Lett. B 544 (2002) 97, Phys. Rev. D 83 (2010) 092001] Test of CPT symmetry invariance [K.A. Olive et al. (Particle Data Group, Chin. Phys. C, 38, 090001 (2014)] Precision test of the CKM unitarity [Eur. Phys. J. C 69 (2010)] Test of lepton universality [Phys. Lett. B 719 (2013) 326] F.Bucci

Anomalies in Kaon Physics: / ’ one of the important actors of 1990s particle physics Strong interplay of QCD and EW penguin contributions New results on hadronic matrix elements of QCD and EW penguin operators leads to a prediction in the SM significantly below experimental data. F.Bucci Buras, Gorbahn, Jager, Jamin ArXiV 1507.06345 World average from NA48 and KTeV  3  discrepancy Impact on various NP models: in particular models where there is a strong correlation between / and the branching ratio for K++ and KL0 Z’ general (Buras, Buttazzo, Knegjens, 1507.08672), Littlest Higgs Model (Blanke, Buras, Recksiegel, 1507.06316), 331 Models (Buras, De Fazio, 1512.02869, 1604.02344)

K in the SM … Flavour Changing Neutral Current process forbidden at tree level in the SM Highest CKM suppression  very sensitive to New Physics Theoretical uncertainties at the level of 2% in BR but significant parametric uncertainties due to |Vub|, |Vcb| and  F.Bucci [Buras et al. arXiv:1503.02693], [Brod et al. Phys. Rev. D 83,034030 (2011)]

… and beyond the SM Pattern of correlation between BR(K++) and BR(KL0) discriminates among models Z model [A. J. Buras, F. De Fazio and J. Girrbach JHEP 1302 (2013) 116] Randall-Sundrum [JHEP 0903 (2009) 108] Littlest Higgs [Acta Phys. Polon. B41 (2010) 657] F.Bucci

The long K march First search: 1969 (10-4) Observation: 1997 (10-10) K++ KL0 F.Bucci KOTO KOTO NA62  [Phys. Rev. D77, 052003 (2008), Phys. Rev. D79, 092004 (2009)]

The NA62 Experiment for K++ SPS proton 400 GeV 1012p/s 3.5 s spill F.Bucci Secondary Beam Momentum 75GeV/c, p/p 1% Divergence (RMS) 100 rad Composition K(6%), (70%), p(23%) Nominal rate 331011 (750 MHz at GTK3) Transverse size 6030 mm2 Decay region Fiducial region 60 m length K+ decay rate  5 MHz Vacuum O(10-6) mbar

The NA62 Status 2014 Pilot run 2015 Commissioning run 2016 Commissioning + Physics run F.Bucci 2016 Run 07/05-22/07 Detector commissioning 23/07-13/09 Final Commissioning /L1 trigger, GTK) Physics (exotics, rare/forbidden decays) 16/09-03/11 Physics (, exotics, rare/forbidden decays)

 Analysis NA62 goal : K++ BR measurement with O(10%) precision O(10%) Signal acceptance O(5/1) Signal/Background On disk ( period, 60m fiducial volume) 131011ppp on T10 (40% of nominal) Intensity and DAQ capability depend on spill quality F.Bucci 2016 Analysis goal : assess the sensitivity at the level of 10% In the next slides a preliminary exploratory analysis shown ( 5% of 2016 data)

 Analysis Strategy Signal signature: Background: Incoming K+ Outgoing p+ in time with the K+ Nothing else Background: K++0 0.2066 K++ 0.6356 K++- + 0.0558 Analysis tools: Precise kinematic reconstruction PID: K upstream, e// downstream Hermetic  detection Sub-ns timing F.Bucci

 Selection NA62 Keystone O (100 ps) Timing between sub-detectors O(104) Background suppression from kinematics > 107 Muon suppression > 107 0 (from K++0 ) suppression K+ Decay Event Fiducial Decay Region Particle ID Photon Rejection Multiple charged particle rejection Kinematic selection of the signal regions F.Bucci

Kaon Decay Selection Single + topology Kaon ID in KTAG K -  matching + timing: (TCHOD)250 ps, (TRICH)100 ps K+ timing: (TKTAG)80 ps, (TGTK)100 ps Closest distance of approach between GTK and Straw track TGTK-TKTAG F.Bucci NA62 Preliminary NA62 Preliminary (CDA)1.5mm Mis-tagging probability:  1.7% [40% nominal intensity, 75% efficiency]

Fiducial Decay Region Origin of Kaon Decays Events K+ decays downstream GTK3 K+ interactions in GTK3 K+ decays upstream GTK3 early decays Fiducial Decay Region 110/115 < Zvertex < 165 m lower limit against early decays CHANTI against interactions in GTK3 F.Bucci

Kinematics F.Bucci

Signal and Background Regions To control non gaussian tails from mis-match and mis-measurements m2miss resolution F.Bucci compute the missing mass also with RICH indipendently from STRAW with nominal K momentum design value reached : 10-3 GeV4/c2

Particle ID Samples of  and  from K++0 and K++ selected kinematically Combined efficiency PID with calorimeters  ID efficiency  80%  mis-ID probability  10-5 NA62 Preliminary PID with RICH  ID efficiency  80%  mis-ID probability  10-2 Efficiency of  ring reconstruction  90% [depends on p ] F.Bucci NA62 Preliminary RICH, calorimeter independent Performances improvement expectd

Photon Rejection To measure  rejection, consider events left in the K++0 region after the  selection Before -rejection minimum bias, D=400 After -rejection PNN trigger NA62 Preliminary NA62 Preliminary  accidental losses measured on K++ F.Bucci events passing signal selection with photon veto = (1.20.2)10-7 Events in control trigger passing the signal selection but the photon veto downscale factor of control trigger

Expected Signal and Background in 5% of 2016 statistics 85% (preliminary) measured on data Normalization: K++0 cfrom control trigger data passing the signal selection but the photon rejection Acceptance: ratio between signal and normalization: 0.60/0.86 N (K decays)  2.3  1010 [5% of 2016 statistics]   acceptance 0.033 F.Bucci Process Expected Events Branching ratio K++0 0.024 0.2066 K++ 0.011 0.6356 K++- + 0.017 0.0558 Early decays < 0.005 K++- + suppression very preliminary

K++ Result No events in signal region F.Bucci Event in box has m2miss (no GTK) outside the signal region

NA62 Physics besides K++ The high-intensity and high-performance setup make NA62 suited for other NP searches Exotic searches Dark Photons (A’), Heavy Neutral Leptons (HNL), Axion-like particles (ALP) Rare/Forbidden Decays K++l+l- [O(10-7)] , 0e+e- [BR=6.4610-8] K++l1+l2-, K+l1-l1+l2- (l1,2= e,), K++e, 0 e F.Bucci

Invisible Vector from 0 decay K++0, 0A’, A’ invisible N(K decays) 1.5  1010 ( 4% 2016 statistics)  mA’ (GeV) F.Bucci

Conclusions Kaons ? New Physics could be already there: ’ ? NA62 fully working Good 2016 run 51011 kaon decays taken in the last 40 days goal: test sensitivity down to 10-10 First preliminary results on K++ (5% data) are promising analysis of the full 2016 data set in progress optimization/improvement of the analysis in progress Excellent prospects for a broader physics program F.Bucci

Spare Slides

RK Final Result RK= (2.488 ± 0.010) 10-5 Fully exploit kinematics and strong particle ID Main background from K2 10 improvement, consistent with SM F.Bucci NP potential still open NA62 prospects: expected uncertainty 0.2% (more statistic, more hermetic vetoing, better resolution and PID) TREK stopped K proposal: expected uncertainty 0.25% KLOE (2009) 14K events, 16% bkg NA62 (2013) 146K events, 11% bkg

KL0→p0nn The charm contribution can be fully neglected since it proceeds in the SM almost entirely through direct CP violation → determination of h Exp Machine Meas. or UL 90% CL Notes KTeV Tevatron <5.710-7(p0→eeg) E391a KEK-PS <2.610-8 KOTO J-PARC Aim at 2.7 SM evts/3y F.Bucci Need a huge number of KL decays NA48 KL flux corresponding to 31010/year NA62 possible KL flux 5-10 times NA48 one After SPS upgrade 100 times more

Anomalies in Kaon Physics: K  Ms,d Tension New results from Fermilab Lattice and MILC collaboration Construct the UUT (CMFV) by using only and derive Strategy 1: Ms determines Vcb  |Vcb| = (39.51.3)10-3 Strategy 2: K determines Vcb  |Vcb| = (39.51.3)10-3 F.Bucci Blanke, Buras 1602.04020 Tension between Ms and K Impact on the branching ratio of K++ and KL0