NA62 status and prospects Cristina Lazzeroni University of - PowerPoint PPT Presentation

NA62 status and prospects Cristina Lazzeroni University of Birmingham on behalf of the NA62UK collaboration PPAP community meeting RAL • 21 July 2017 Outline: • Physics at kaon experiments: K →πνν νν decays and beyond • NA62 status, performance, UK involvement. • Physics exploitation programme for 2021-2024. • Overview of the recent results. • Summary 0

CERN kaon kaon experiments experiments CERN Kaon decay-in-flight experiments at CERN: NA62 : currently ~200 participants, ~30 institutions. NA62UK: Birmingham, Bristol, Glasgow, Liverpool--->Lancaster 1 (12% of participants)

Rare kaon decays: K →πνν Rare kaon decays: K →πνν SM: box and penguin diagrams SM branching ratios Ultra-rare decays with Buras et al., JHEP 1511 (2015) 033 the highest CKM suppression: BR SM × 10 11 Mode A ~ (m t /m W ) 2 |V ts V td | ~ λ 5 * K + →π →π + νν νν ( γ ) 8.4 ± 1.0 K L →π →π 0 νν 3.00 ± 0.31 νν  Hadronic matrix element related The uncertainties are largely to a measured quantity ( K + →π →π 0 e + ν ). parametric (CKM)  Exceptional SM precision.  Free from hadronic uncertainties. Theoretically clean,  Measurement of |V td | complementary almost unexplored, to those from B − B mixing or B 0 →ρ →ργ . sensitive to new physics. 2

K →πνν : experiment xperiment vs vs theory theory K →πνν : e CKM unitarity triangle with kaons BR(K L →π 0 νν ) vs BR(K + →π + νν ) Current experimental uncertainty (littlest Higgs D. Straub with T parity ) CKM 2010 NA62 aim: collect O(100) SM K + →π + νν decays using a novel decay-in-flight technique. 3

NA62 broad physics programme programme(I) (I) NA62 broad physics NA62 approach allows for a broad physics programme: Signature: high momentum K + ( 75GeV/c )  low momentum π + ( 15 − 35 GeV/c ). Advantages: max detected K + decays/proton ( p K /p 0 ≈ 0.2 ); efficient photon veto ( >40 GeV missing energy) Un-separated beam ( 6% kaons)  higher rates, additional background sources.  NA62 Run 2016 − 2018 : focused on the “golden mode” K + →π νν . →π + νν  Several measurements at nominal SES~10 − 12 : K + →π →π + A’ , π 0 →ν →νν .  A few measurements do not require extreme SES: K + → ℓ + N , …  Sensitivities to most rare/forbidden decays are limited but still often world-leading ( ~10 − 10 to ~10 − 11 ).  Proof of principle for a broad rare & forbidden decay programme. 4

NA62 broad physics programme programme(II) (II) NA62 broad physics  NA62 Run 2021 − 2024 : continue physics exploitation , make the most of previous investments. Commitment of UK groups to NA62 physics programme. [Presented at Physics Beyond Colliders workshops, CERN, Sep 2016 & Mar 2017]  Existing apparatus with improved trigger logic.  Evaluate incremental changes for optimal efficiency.  Further K + →π νν data collection. →π + νν  Rare/forbidden K + and π 0 decays at SES~10 − 12 : K + physics: K + →π →π + ℓ + ℓ − , K + →π →π + γ ℓ + ℓ − , K + → ℓ + νγ νγ , K + →π →π + γγ γγ , … π 0 physics: π 0 → e + e − , π 0 → e + e − e + e − , π 0 → 3 γ , π 0 → 4 γ , … Searches for LFV/LNV: K + →π →π − ℓ + ℓ + , K + →π →π + µ e , π 0 → µ e , …  Beam dump with ~10 18 POT : hidden sector (long-lived HNL, DP, ALP). UK-led recent results and prospects on exotics: 1. Searches for heavy neutral leptons: K + → µ + ν 2. Searches for heavy neutral leptons: K + → e + ν 3. 3-tracks K + decays 5

NA62 status and UK involvement 6

NA62 collaboration, The NA62 detector The NA62 detector JINST 12 (2017) P05025 Un-separated hadron (p/ π + /K + ) beam. SPS protons: 400 GeV, 3 × 10 12 /spill. Hadronic LAV: large-angle Muon K + : 75GeV/c (±1%), divergence < 100 µ rad. calorimeter photon veto (12 stations) detector 800 MHz beam rate; 45 MHz K + rate; σ t =70ps (MUV) ~5 MHz K + decays in fiducial volume Dump NA62UK GTK: beam tracker KTAG: Cherenkov kaon tagger, σ t =70ps Small-angle Spectrometer: Anti-counters straw chambers photon veto LKr EM calorimeter Z [m]  Expected single event sensitivity for K + decays: BR~10 − 12 .  Measured kinematic rejection factors (limited by beam pileup & MCS tails): 6 × 10 − 4 for K + →π →π + π 0 , 3 × 10 − 4 for K → µ + ν .  Hermetic photon veto: measured π 0 →γ →γγ decay suppression = 1.2 × 10 − 7 .  Particle ID (RICH+LKr+HAC+MUV): ~10 − 7 muon suppression. 7

Beam tracker: the Gigatracker Gigatracker Beam tracker: the Beam profile at GTK y [mm] x [mm] Tracker design: GTK − KTAG timing Arbitrary units  Three Si pixel stations in the beam. with K 3 π decays  Operation at beam rate up to 800 MHz .  In total, 54k pixels ( 300 × 300 µ m 2 ). Matched beam track  Thickness: <0.5% X 0 per station. Performance at 40% beam intensity: Random  Track reconstruction efficiency: 75% . out-of-time  Time resolution σ (t BeamTrack ) ≈ 100 ps . beam track  Beam track mis-tagging probability: 1.7% .  Spatial matching: beam/downstream track intersection, σ CDA ≈ 1.5 mm .

KTAG operation KTAG operation The first NA62 detector to be commissioned; performance exceeds specifications N 2 pressure scan π + p K + Funded by ERC Arbitrary scale PMT time Number of PMT Single PMT. 95% resolution signals per K + Central peak: Mean hits/K + : 20 160ps; σ (K time) working point: Mean nominal RMS=300ps. = 70ps 5-fold coincidence rate/channel: 2.3 MHz Kaon ID efficiency scattering in vs sectors in 1 st dynode coincidence [ns] 0 10 20 30 40 50 60 − 2 − 1 0 1 2 1 2 3 4 5 6 7 8 E. Goudzovski / Birmingham, 26 July 2016

UK participation in NA62 UK participation in NA62 UK participation in NA62 from 2011:  Capital funding and manpower for detector construction and operation from ERC / EU and Royal Society Grants. (manpower: 6 postdocs, 1 RS fellow, academic time)  Soon after, STFC contribution with M&O costs.  Now in exploitation mode : supported by STFC Particle Grant.  Extremely good value for STFC investment : M&O, 1 postdoc, 2 Rutherford fellows, travel, some academic time.  Strong, wide-spread leadership. 10

NA62: UK contributions NA62: UK contributions Hardware and trigger:  full responsibility for the KTAG subdetector ;  full responsibility for the Run Control system;  development and operation of L0 muon+hodoscope+RICH trigger ;  development and operation of the high-level software trigger ;  GRID infrastructure, software, data processing ;  DCS system . Leadership in the physics exploitation:  Flagship analysis: K + →π →π + νν νν ;  Detector performance studies with data;  Rare decays and forbidden studies:  Analyses of “old” NA48/NA62 data. Major leadership roles:  Physics coordination ;  Computer coordination ;  LFV, π + νν νν WGs coordination ;  Run coordinators : 3 out of 12 (in 2017);  High-level trigger coordination ;  Editorial Board membership: 4 out of 10;  2 out of 4 PBC representatives;  Conference Committee chair. UK groups have been consistently responsible for >50% of the physics output of NA62 11

Data collection Data collection  Commissioning run 2015 : minimum bias ( ~1% intensity) and K πν πνν test data.  Most systems commissioned and meet the design requirements  First high intensity run: 3 May − 14 November 2016  Data collection at ~40% of the nominal intensity (limited by beam quality)  Long (~6 months) runs in 2017 (started in May) and 2018 Reached sensitivity of ~1 SM K πν πνν event with the 2016 data 12

High intensity run in 2016 High intensity run in 2016 1.4 × 10 12 NA62 integrated number of Beam frequency spectrum K + decays (2016) 1.2 × 10 12 DAQ capability is All beam tracker stations limited by the maximum 10 12 fully operational: data instantaneous intensity for K πν πνν (~50% of total) 8 × 10 11 Looks much better Integrated kaon flux in 2017 6 × 10 11 higher than NA48/2 4 × 10 11 2 × 10 11 50 100 150 200 250 Date [day/month] Frequency [Hz]  Stable data collection at ~40% of the nominal intensity; limited by beam structure, including the 50 Hz harmonics.  Simultaneous data taking for K πν πνν and rare/exotic decays .  Extrapolation to end of 2018 (12 months of live time): 7 × 10 12 K + decays.  With improved extraction and incremental improvements in efficiency, the target of 10 13 K + decays by end of 2018 is reachable. 13

K πνν signal region definition ignal region definition K πνν s m miss 2 =(P K − P π ) 2 vs track momentum; Main K + decay modes ( >90% of BR) rejected DATA 2016 decays in fiducial decay region kinematically. K + →π →π + π + π − K + →π →π + π 0 π 0 Design kinematical resolution on m miss 2 Minimum bias trigger has been achieved ( σ =1.0 × 10 − 3 GeV 4 /c 2 ). Region II K + →π →π + π 0 Measured kinematical K + → µ + ν background suppression: Region I  K + →π →π + π 0 : 6 × 10 －4 ;  K + → µ + ν : 3 × 10 －4 . Further background suppression:  PID (calorimeters & Cherenkov detectors): µ suppression <10 − 7 . Analysis done in 3D space:  Hermetic photon veto: suppression of m 2 miss , m 2 miss (RICH), m 2 miss (no GTK) →γγ decays <10 − 7 . π 0 →γ