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Recent results from NA62 experiment

23.08.2013

16th Lomonosov conference Moscow, 22-28.08.2013

V.Duk, for the NA62 collaboration

Viacheslav Duk, INFN Perugia For the NA62 collaboration

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Plan 1. 2. 3. 4. 5. 6. 7. NA62 biography Rare kaon decays Results from 2007-2008 run K decay Experimental setup Beyond the baseline Conclusions

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NA62 biography

NA62 main goal: measure K++ decay (~100 events with S/B~10)
B eyond the baseline: Decays with LFV Heavy neutrinos 0 decays

NA62 collaboration: Birmingham, Bratislava, Bristol, CERN, JINR Dubna, Fairfax, Ferrara, Florence, Frascati, Glasgow, IHEP Protvino, INR Moscow, Liverpool, Louvain-la-Neuve, Mainz, Merced, Naples, Padua, Perugia, Pisa, Prague, Rome I, Rome II, San Luis PotosМ, Sofia, Stanford, Turin
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Rare kaon decays
Do we still need kaon physics in the LHC era?

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Rare kaon decays
Message from A.Buras for NA62 and others

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Results from 2007-2008 run
RK = BR(Ke2()) / BR(K()) measurement: Motivation: Lepton flavor universality test Best statistics (145958 events of Ke2 decay) ~0.4% accuracy achieved Result: RK = (2.488 ± 0.007stat ± 0.007syst) x 10 (in accordance with SM predictions)

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K decay: Motivation: ChPT tests Best statistics (~300 events, combined with 2003-2004 run) Result: ChPT O(p4) and O(p6) cannot be distinguished Model-independent BR measurement with accuracy <10% Details: see talk by Andrea Bizzeti on August 27
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K decay
Golden kaon modes
FCNC process: · Forbidden at tree level · Box and penguin diagrams · Small BR (5 suppression)

Theoretically clean (~10%) Main contribution from Short Distance 2-loop EW corrections below 1% Hadronic matrix elements related to well known decay K+e+0 Sensitive to New Physics Experimental result: E787/E949 (BNL)
23.08.2013 V.Duk, for the NA62 collaboration

Parametric error (Vcb, measurements) theoretical error (LD corrections)
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K decay: measurement principles
main kinematic variable: Mmiss2 = (PK ­ P)2

2 signal regions split by the K2 peak: 92% background decays outside kinematical region 8% background should be rejected by vetoes and PID

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Experimental setup

Basic principles: Decays-in-flight technique (60m decay volume, ~10% decayed kaons) High intensity, fast timing Kinematic reconstruction particle ID Efficient veto ~10% acceptance
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Experimental setup: kaon measurement

Beam: 400 GeV/c protons from SPS 3 x 1012 protons per pulse on target 75 GeV/c secondary beam ~6% of K+ (unseparated beam) 750MHz @ beam tracker 10MHz downstream 4.8 x 1012 kaon decays per year

KTAG/Cedar: Differential Cherenkov counter for kaon ID High rate environment H2 at 3.6 bar ~100ps time resolution

GTK: 3 Si pixel stations 300 x 300 m pixels Very thin (~0.5X0 per station) p/p ~ 0.2% 200ps per station time resolution

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Experimental setup: pion measurement

Straw: 4 straws in vacuum Spectrometer magnet (256 MeV/s kick) p/p <1% 66 rad

RICH: Ne at atmospheric pressure - separation at ~1% for 15 < P < 35 GeV/c Time resolution ~100 ps L0/L1 trigger signals

CHOD:

2 planes with 128 scintillator slabs read by PMs L0 trigger signal

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Experimental setup: photon veto systems

LAV: 12 stations in vacuum Cover 8.5 to 50 mrad OPAL lead glass read by PMs ~18.6 X0

LKr: NA48/2 em calorimeter Cover 1 to 8.5 mrad ~27 X0 detection inefficiency for E>10 GeV: (1-) < 8x10 100ps time resolution

IRC & SAC: Small angle calorimeters Cover <1 mrad
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LAV+LKr+IRC+SAC: ~108 rejection of 0
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V.Duk, for the NA62 collaboration


Experimental setup: veto systems

CHANTI: 6 station GTK3 Identify inelastic Identify

s after upstream interactions muon halo

MUV1 & MUV2: Iron/scintillator sandwich calorimeter

MUV3: Iron wall + scintillator Light read by PMs Fast trigger signals

MUV+RICH: ~107 muon rejection
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Experimental setup: trigger
L0: Hardware trigger RICH+CHOD+!LKr+ !MUV3 L1: Software trigger "single detector"

L2: Software trigger Correlations between detectors

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Status of the experiment

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Partial setup: LKr, Cedar/KTAG, CHOD, MUV2, MUV3 TR goals: Tests of readout electronics, detector, infrastructure K2 reconstruction

Technical Run 2012
Time distirbutions wrt Cedar/KTAG
CHOD LKr

MUV3

MUV2

detector Cedar/KTAG LKr

Resolution (ps) 150 350

CHOD
MUV3
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400 (240 after time corrections)
450
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V.Duk, for the NA62 collaboration


Beyond the baseline: search for LFNV decays
0 tagged from K2 decay 2 years of data taking: 1.2 x 1013 K+ decays 2.5 x 1012 0 decays

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Beyond the baseline: heavy
Search for heavy : peak in KN decay NA62: 18M K2 data sample (2007-2008 run) UL if no backgrounds: |UN|2 < 10-7 Sensitivity limited by background subtraction Prospects for high masses

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conclusions
NA62 is a challenging kaon experiment The main goal is to measure K++ with 10% precision Other goals: LFNV searches in K+ and 0 rare decays Extensive setup tests were performed during Technical Run 2012 NA62 will start data taking in the end of 2014

THANK YOU!

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Spares

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Background budget

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RK measurement

NP:

Ke2 sample

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K decay: NP contributions

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0 decays: U boson search

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0 decays: 0 invisible

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