COMMISSIONING AND FIRST RESULTS OF THE NA62 RICH

Transcription

1 Siena th Topical Seminar on Innova4ve Par4cle and Radia4on Detectors (IPRD16) 3-6 October 2016 Siena, Italy COMMISSIONING AND FIRST RESULTS OF THE NA62 RICH M. LENTI INFN Sezione di Firenze On behalf of the NA62 RICH WG

2 Outlook The NA62 experiment The RICH Detector ConstrucJon and Commissioning Time ResoluJon Pion-Muon separajon Conclusions 3/10/16 M. LenJ 2

3 The NA62 Experiment NA48 ( ): K L /K S beams èdirect CPV Measurement NA48/1 (2002): K S beam è K S rare decays NA48/2 (2003-4): K + /K - beams è K ± precise measurement NA62 (2007-8): K + /K - beams èlepton Universality K e2 /K µ2 NA62 (2014-8): K + beam èbr(k + π + νν), new physics, rare decays, etc NA62: 200 parjcipants, 30 InsJtutes 3/10/16 M. LenJ 3

4 The NA62 Goal FCNC loop process Very clean theorejcally SM predicjon BR( K + π + νν ) = ( 8.4 ±1.0) Experiments BR K + π + νν K + π + νν ( ) = NA62: 100 events, 10% error [ ] ( ) BNL E949 ( ) 3/10/16 M. LenJ 4

5 1 m Detectors for Secondary Beam Kaon ID (KTAG) Beam Tracker Beam guard ring (CHANTI) The NA62 Setup CHANTI Large Angle E.M. Calorimeters Hadron Calorimeters Forward E.M. Calorimeter (LKR) Momentum selecjon and collimajon KTAG Beam tracker RICH Straw Spectrometer Small Angle E.M. Calorimeters SPS protons 400 GeV p/s 3.5 s spill Secondary Beam 75 GeV, Δp/p 1% X,Y Divergence < 100 µrad K(6%),π(70%),p(23%) Total rate: 750 MHz Beam size: cm 2 Kaon Decay 5 MHz /year 60 m length 10-6 mbar vacuum Detectors for Decay Products Charged ParJcle Tracking Charged ParJcle Time stamping Photon DetecJon ParJcle ID 3/10/16 M. LenJ 5

6 The RICH Detector PMTs Mirror Mosaic (17m focal length) Beam Vessel: 17 m long, filled with Neon µ contaminajon < 1% in π sample in 15<p<35 GeV/c Time resolujon < 100 ps L0 trigger for a charged track 3/10/16 M. LenJ 6

7 The RICH Detector (since 2014) 3/10/16 M. LenJ 7

8 The Cherenkov Radiator Neon gas slightly above atmospheric pressure (n-1)= at λ = 300 nm P threshold = 12.5 GeV/c for π good light transparency Low chromajc dispersion Fresh Neon injected aler RICH container evacuated: no purificajon/recirculajon system 3/10/16 M. LenJ 8

9 The Gas Container ( Vessel ) Vacuum proof tank 17 m long in construcjon steel 4 cylindrical secjon of decreasing diameter and different lengths Beam pipe (Ø 168 mm) going through Thin Al entrance and exit windows View from inside, looking upstream towards the PMTs 3/10/16 M. LenJ 9

10 The Mirror System Mosaic of 20 spherical mirrors (18 hexagonal, 2 semi-hex close to the beam pipe) to focus Cherenkov light to the PMTs plane 2.5 cm thick glass coated with Al with dielectric film 35 cm side length Radius of curvature: (34.0±0.2) m Average reflecjvity 90% ( nm) D 0 < 4 mm (opjcal quality parameter) 3/10/16 M. LenJ 10

11 Mirrors Support and Alignment Al honeycomb support structure Each Mirror supported by a dowel inserted in the back Two thin Al ribbons keep the mirror in equilibrium and allow its orientajon A third verjcal ribbon avoid rotajon Piezo motors allow remotely controlled orientajon 3/10/16 M. LenJ 11

12 Mirrors Alignment Preliminary Laser alignment before closing the vessel Final alignment using charged tracks during data taking (reconstructed by the spectrometer) Compare the posijon of the ring center on the PMTs plane with posijon predicted by track extrapolajon Select rings fully contained in a single mirror (Y ring -Y ref )(mm) Jura (Y ring -Y ref )(mm) Saleve All mirrors Aligned within 1 mm ( 30 µrad) With respect to The reference Each cross is one mirror (X ring -X ref )(mm) (X ring -X ref )(mm) 3/10/16 M. LenJ 12

13 The PhotoMulJpliers Cherenkov light reflected by the mirrors is collected by 1952 PMTs located in two spots Compact hexagonal packing 18 mm pixel size Hamamatsu R7400-U03 UV glass window, 16 mm Ø (8 mm acjve Ø) Custom made HV divider SensiJve range nm (420 nm peak) Gain at 900 V Q.E. 20% at peak 280 ps Jme jiuer (FWHM) Winston cones with Al mylar to opjmize light collecjon Quartz window separate Neon from air TDAQ system bastem on custom made FE boards and TEL62 3/10/16 M. LenJ 13

14 Front-End and Read-Out RICH front-end 64 Custom-made boards 8-ch NINO chip discriminators 32-ch boards (3 NINO each) RICH read-out 128-ch TDC daughter boards (TDCB) each with 4 CERN HPTDC 5 TEL62 mother boards (4 for the 1952 PMTs, 1 for the muljplicity read-out used for L0 trigger) each with 4 TDCBs 3/10/16 M. LenJ 14

15 Time ResoluJon The RICH event Jme resolujon is 70 ps Detected photons (hits) of one Cherenkov ring split in two sets Time difference of Jme average of each set is ploued Time resolujon is ½ σ Cherenkov ring average Jme compared with KTAG Jme 3/10/16 M. LenJ 15

16 RICH ParJcle ID Charged pions, muons and electrons selected with calorimetric and spectrometer info <N hits > Number of hits per Cherenkov ring vs p e + µ + Radius (mm) Cherenkov ring Radius vs p π + p(gev/c) Kaons from scauered beam p(gev/c) 3/10/16 M. LenJ 16

17 π-µ separajon For 86% π ID efficiency a 1.3% µ mis-id efficiency is observed Squared parjcle mass reconstructed using velocity (from RICH ring Radius) and momentum (from spectrometer) Pion idenjficajon efficiency vs Muon mis-idenjficajon Efficiency for π ID m 2 (GeV 2 /c 4 ) Efficiency for µ mis-id 3/10/16 M. LenJ 17

18 2016 Preliminary Results For 90% π ID efficiency a 0.8% µ mis-id efficiency is observed Efficiency for π ID 2016 Preliminary Results Beuer mirror alignment in 2016 w.r.t Efficiency for µ mis-id 3/10/16 M. LenJ 18

19 Conclusions NA62 RICH detector installed in 2014 Pilot Run in fall 2014 Commissioning run in 2015 Detector upgrade in the winter shutdown Physics Run in 2016 RICH performances fufilling expectajon NA62 running unjl (at least) end of /10/16 M. LenJ 19

20 NA62 3/10/16 M. LenJ 20