Anomalies in Kaon Physics the NA 62 program

Anomalies in Kaon Physics: the NA 62 program Francesca Bucci (INFN, Sezione di Firenze) on behalf of NA 62 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

• 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 K 0 mixing [Phys. Rev. Lett. 13 (1964) 138] • 3 -quark-model to describe the observed meson/baryon spectra [Phys. F. Bucci Kaon Physics: a Building Block of the SM 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 K 0 [Phys. Lett. B 206 (1988) 169] 2

Kaon Physics: Toward the Present Era Kaon Experiments [1995 -2010] • Measurement of direct CP violation in the K 0 (NA 48@CERN, KTe. V@FNAL) F. Bucci NA 48 (CERN), KTe. V (FNAL), KLOE (LNF), CPLEAR (CERN), E 865 (BNL), ISTRA+ (Protvino) [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] 3

Anomalies in Kaon Physics: / F. Bucci • ’ one of the important actors of 1990 s 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. Buras, Gorbahn, Jager, Jamin Ar. Xi. V 1507. 06345 World average from NA 48 and KTe. V 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) 4

K 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 Flavour Changing Neutral Current process forbidden at tree level in the SM [Buras et al. ar. Xiv: 1503. 02693], [Brod et al. Phys. Rev. D 83, 034030 (2011)] 5

… and beyond the SM Pattern of correlation between BR(K+ + ) and BR(KL 0 ) discriminates among models Z model Randall-Sundrum [JHEP 0903 (2009) 108] F. Bucci [A. J. Buras, F. De Fazio and J. Girrbach JHEP 1302 (2013) 116] Littlest Higgs [Acta Phys. Polon. B 41 (2010) 657] 6

The long K march First search: 1969 (10 -4) Observation: 1997 (10 -10) KL 0 F. Bucci K+ + NA 62 KOTO 7 [Phys. Rev. D 77, 052003 (2008), Phys. Rev. D 79, 092004 (2009)]

+ + The NA 62 Experiment for K F. Bucci SPS proton 400 Ge. V 1012 p/s 3. 5 s spill Secondary Beam Momentum Decay region 75 Ge. V/c, p/p 1% Divergence (RMS) 100 rad Composition K(6%), (70%), p(23%) Nominal rate 33 1011 (750 MHz at GTK 3) Transverse size 60 30 mm 2 Fiducial region 60 m length K+ decay rate 5 MHz Vacuum O(10 -6) mbar 8

2014 Pilot run 2015 Commissioning run 2016 Commissioning + Physics run 2016 Run 07/05 -22/07 Detector commissioning 23/07 -13/09 Final Commissioning /L 1 trigger, GTK) Physics (exotics, rare/forbidden decays) 16/09 -03/11 Physics ( , exotics, rare/forbidden decays) F. Bucci The NA 62 Status 9

Analysis NA 62 goal : K+ + BR measurement with O(10%) precision O(10%) Signal acceptance � O(5/1) Signal/Background On disk ( period, 60 m fiducial volume) 13 1011 ppp on T 10 (40% of nominal) Intensity and DAQ capability depend on spill quality 2016 Analysis goal : assess the sensitivity at the level of 10% In the next slides a preliminary exploratory analysis shown ( 5% of 2016 data) F. Bucci � 10

Analysis Strategy Background: K+ + 0 0. 2066 K+ + 0. 6356 K+ + - + 0. 0558 F. Bucci Signal signature: • Incoming K+ • Outgoing + in time with the K+ • Nothing else Analysis tools: • Precise kinematic reconstruction • PID: K upstream, e/ / downstream • Hermetic detection • Sub-ns timing 11

NA 62 Keystone O (100 ps) Timing between sub-detectors O(104) Background suppression from kinematics > 107 Muon suppression > 107 0 (from K+ + 0 ) suppression F. Bucci Selection � K+ Decay Event Fiducial Decay Region � Particle ID � Photon Rejection � Multiple charged particle rejection � Kinematic selection of the signal regions � 12

Kaon Decay Selection Closest distance of approach between GTK and Straw track ry ina m i l e r 2 P NA 6 (CDA) 1. 5 mm + timing: (TCHOD) 250 ps, (TRICH) 100 ps K+ timing: (TKTAG) 80 ps, (TGTK) 100 ps TGTK-TKTAG NA 6 F. Bucci • Single + topology • Kaon ID in KTAG • K - matching ry ina m i l e r 2 P 13 Mis-tagging probability: 1. 7% [40% nominal intensity, 75% efficiency]

Origin of Kaon Decays Events • K+ decays downstream GTK 3 • K+ interactions in GTK 3 • K+ decays upstream GTK 3 early decays F. Bucci Fiducial Decay Region 110/115 < Zvertex < 165 m • lower limit against early decays • CHANTI against interactions in GTK 3 14

F. Bucci Kinematics 15

Signal and Background Regions To control non gaussian tails from mis-match and mis-measurements F. Bucci m 2 miss resolution design value reached : 10 -3 Ge. V 4/c 2 compute the missing mass also • with RICH indipendently from STRAW • with nominal K momentum 16

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 nary imi l e r P 62 F. Bucci NA PID with RICH • ID efficiency 80% • mis-ID probability 10 -2 • Efficiency of ring reconstruction 90% [depends on p ] ary NA imin l e r P 62 17 RICH, calorimeter independent Performances improvement expectd

Photon Rejection To measure rejection, consider events left in the K+ + 0 region after the selection NA nary i m i l e 62 Pr After -rejection PNN trigger ary imin l e r P 62 NA events passing signal selection with photon veto downscale factor of control trigger Events in control trigger passing the signal selection but the photon veto accidental losses measured on K+ + = (1. 2 0. 2) 10 -7 F. Bucci Before -rejection minimum bias, D=400 18

Expected Signal and Background in 5% of 2016 statistics 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 F. Bucci 85% (preliminary) measured on data N (K decays) 2. 3 1010 [5% of 2016 statistics] acceptance 0. 033 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 19

+ + K Result F. Bucci No events in signal region 20 Event in box has m 2 miss (no GTK) outside the signal region

NA 62 Physics besides K+ + The high-intensity and high-performance setup make NA 62 suited for other NP searches Rare/Forbidden Decays K+ +l+l- [O(10 -7)] , 0 e+e- [BR=6. 46 10 -8] K+ +l 1+l 2 -, K+ l 1 - l 1+l 2 - (l 1, 2= e, ), K+ + e , 0 e F. Bucci Exotic searches Dark Photons (A’), Heavy Neutral Leptons (HNL), Axion-like particles (ALP) 21

Invisible Vector from 0 decay K+ + 0, 0 A’ , A’ invisible N(K decays) 1. 5 1010 ( 4% 2016 statistics) F. Bucci m. A’ (Ge. V) 22

Conclusions Kaons ? New Physics could be already there: ’ ? • Good 2016 run 5 1011 kaon decays taken in the last 40 days goal: test sensitivity down to 10 -10 F. Bucci • NA 62 fully working • 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 23 Excellent prospects for a broader physics program

Spare Slides

RK Final Result RK= (2. 488 ± 0. 010) 10 -5 F. Bucci Fully exploit kinematics and strong particle ID Main background from K 2 10 improvement, consistent with SM KLOE (2009) 14 K events, 16% bkg NA 62 (2013) 146 K events, 11% bkg NP potential still open NA 62 prospects: expected uncertainty 0. 2% (more statistic, more hermetic vetoing, better resolution and PID) TREK stopped K proposal: expected uncertainty 0. 25% 25

KL 0→ 0 The charm contribution can be fully neglected since it proceeds in the SM almost entirely through direct CP violation → determination of h Machine Meas. or UL 90% CL KTe. V Tevatron <5. 7 10 -7( 0→ee ) E 391 a KEK-PS <2. 6 10 -8 KOTO J-PARC Need a huge number of KL decays NA 48 KL flux corresponding to 3 1010/year NA 62 possible KL flux 5 -10 times NA 48 one After SPS upgrade 100 times more Notes F. Bucci Exp Aim at 2. 7 SM evts/3 y 26

Anomalies in Kaon Physics: K Ms, d Tension • Construct the UUT (CMFV) by using only F. Bucci • New results from Fermilab Lattice and MILC collaboration and derive Blanke, Buras 1602. 04020 Strategy 1: Ms determines Vcb |Vcb| = (39. 5 1. 3) 10 -3 Strategy 2: K determines Vcb |Vcb| = (39. 5 1. 3) 10 -3 Tension between Ms and K Impact on the branching ratio of K+ + and KL 0 27