J-Parc E14. K L π 0 νν. Taku Yamanaka Osaka Univ. Jul. 6, 2007 J-Parc KEK

Transcription

1 J-Parc E14 K L π 0 νν Taku Yamanaka Osaka Univ. Jul. 6, 2007 J-Parc KEK

2 s W t d J-Parc E14 Z 0 ν Physics Measure the CKM eta and probe new physics beyond the standard model. Goals Step 1: First observation of the decay η s + χ ũ KL π 0 νν ν d ν ν Step 2: Measure BR to <10% B J/ψK S ρ

3 Outline Status of KEK PS E391a Schedule Budget and manpower Request and Summary Summary of FIFC reports

4 Status of KEK PS E391a Run-2 FULL data sample

5 KL decays We understand detector performance K L->3pi0 background under KL->2pi0 orimeter and applied selection criteria (cuts) to s background events. In Run-1, the downstream ne was partially hanging in the beam by error, at ecause neutrons in the beam core struck the mem- M 4γ (GeV/c ) FIG. 4 (color online). Distribution of the invariant mass (left) Kaon Mass with All Cuts and the decay vertex (right) for the KL 0! 0 0 Decay Z-Vertex (All Cuts) Four Cluster Invariant Mass decays. In the FIG. 2. Distribution of the invariant mass of four photons, 10 top plot, the dots show the data and the histogram shows 3 the MC. 10 The cm. bottom This Run produced II plot shows athelarge ratio number of the data oftobackground M 4, with the cuts on the photon 3 Run vetoiidetectors! and 0! the 0! 0 shower MC 10 3 the MC. 10 shape of photons in the CsI calorimeter. The dots show data, the 2 10 d produced 2 secondary 0 s. If multiple 0 s were open solid histogram shows total MC, the closed solid! 0! histogram 0 MC shows KL 0! MC and the hatched histogram shows KL 0! MC. Data d at the membrane, and two photons from different re detected 1 ( core neutron multi- 0 event), 1 it a serious background event because we were not GeV/c reconstruct Z vtx correctly A and these events4 were 2.25 A ted in 2 the fiducial region. On the other hand, these ad 1.5 extra photons in the final state, and thus2.5can be sed by detecting those extra photons er0.75 to suppress events involving extra photons, 1 we energy 0.25 deposit in each photon veto detector to be n the threshold listed in Table I. The rejection Data / MC Ratio Run II cm the cuts on the photon veto detectors. With all the photon veto cuts, the ratio of the number of KL 0! 0 0 events in 0:45 M 4 GeV=c 2 1 0:55 to the number of KL 0! events in M 4 GeV=c 2 0:45 improved by a factor of 11. This improvement 10-1 was consistent with the expectation of GEANT-3 based [13] Monte Carlo simulation (MC) within 18%. A E-01 A E E Data / MC Ratio GeV/c 2

6 Halo neutron background Run 2 full data sample data MC Pt(GeV/c) CC02 Charged Veto data z(cm)

7 ~1 event based on bifurcation study w/o photon veto Halo n bkg from downstream Pt(GeV/c) N_exp. = 0.4±0.4 Data N_exp. = 0.2±0.2 N_obs. = 3 (CC02 events) N_exp. = 0.3±0.3 N_obs. = 0 N_exp. = 0.61±0.30 N_exp. = 0.53±0.20 N_obs. = 1 N_exp.(halon) =2.3±0.3 N_obs. = z(cm)

8 Halo n bkg from upstream Use special run w/ Al plate in beam, and used its z shape neutron π 0 γγ Al target 2.3±0.3 events w/new z cut original signal region Pt(GeV/c) Al plate run #BG events z(cm) z(cm) 0

9 Sensitivity Pt(GeV/c) single event sensitivity! ~ 1.54 x 10-8 for Run 2-9 exp.ed SES ! z-vertex(cm) exp.ed U.L. by FC method z(cm) z(cm)

10 η background? η (m=548mev/c 2 ) γγ (BR=40%) halo neutron + charged veto around the beam produces η? Reconstructed z vertex

11 without R-z cut to enhance eta #events in low PT region agrees within <2 Pt(GeV/c) Data Entries 2560 Mean x Mean y RMS x 145 RMS y Integral Pt(GeV/c) eta MC Entries Mean x Mean y RMS x 56.8 RMS y Integral 1.533e evts evts z(cm) z(cm) 4 2 0

12 The J-Parc E14

13 Improved beamline J-Parc E14 CsI: 7x7x30 ==> 2.5x2.5x50 cm3 Waveform digitization for rates and cost Upgraded veto counters

14 E14 Basic Strategies 1. Suppress and control backgrounds based on the E391a experience 1.1. Halo neutron backgrounds 1.2. KL backgrounds 2. Make detector capable of handling high rates

15 E14 Strategy 1.1 Suppress halo neutron bkg 1. Reduce beam halo; 1. halo n/kl = halo n/core n (< 10-5 ) x core n / KL (<10)

16 FIFC: Beamline

17 1 design chosen by quick MC X(mm) Neutron density (particles/cm 2 ) ID Entries Mean RMS Z(mm) Radius (cm)

18 Geant4 simulation for halo neutrons 2x104 halo neutrons/pulse (2E14) Neutron profile at CC02 Neutron profile at the CsI Neutron Density (particles/cm 2 ) x10-5 CC02 Neutron Density (particles/cm 2 ) x Radius at CC02 (cm) Radius at CsI (cm)

19 core n / KL n / K ~ 7 (T n > 1GeV); << 40@E391a due to large targeting angle (16deg) particles detailed simulation proposal [1] K L n (E n > 0.1GeV) n (E n > 1.0GeV) γ (> 2MeV) γ (> 10MeV) γ (> 100MeV) < 10 6 < 10 6

20 K1.1 duct 5mm thick SUS beam duct for K1.1 does not affect the halo, but reduces the K and n by x1/2. Thinner window is necessary Counts Neutron Density (particles/cm 2 ) absorber K1.1 duct GeV Neutron Momentum (GeV/c) cm Radius (cm)

21 E14 Strategy 1.1 Suppress halo neutron bkg 1. Reduce beam halo; halo/core < Reduce pi0 and eta production 1. Lower neutron momentum E391a E14 neutrons that produced eta

22 E14 Strategy 1.1 Suppress halo neutron bkg 1. Reduce beam halo; halo/core < Reduce pi0 and eta production 3. Detect halo neutron interaction and veto 1. Neutron Collar Counter (segmented CsI) $ 4 B 8 E A M. H J * = H H A? * = H H A > * = H H A = 1 A H 4 A = H B % B & B B * - ) B $ B! B # B " " 5 A 8 E A M $ # & E

23 NCC Suppresses and vetoes pi0 bkg R(cm) E391a pi0 prouduction points R(cm) E Z(cm) Z(cm) 0 Figure 41: The source position of remaining events in case of CC02 (left) and Counter Generated π 0 in CAL After veto In the signal box CC NCC

24 NCC can measure halo neutron profile and energy spectrum Neutron detection efficiency Efficiency Kinetic Energy(MeV) Efficiency E-cut R-cut R(cm) Figure 44: Neutron tagging efficiency as a function of neutron energy Cut set ɛ n ɛ K Ratio (ɛ n /ɛ K ) K L contamination E-cut 6.3% 0.1% % R-cut 2.9% 0.08% %

25 E14 Strategy 1.1 Suppress halo neutron bkg 1. Reduce beam halo; halo/core < Reduce pi0 and eta production 3. Detect halo neutron interaction and veto 4. Localize background by better calorimeter resolutions

26 KTeV CsI Calorimeter 30cm -> 50cm reduces energy response tail due to shower leakage 7cm -> 2.5cm square position resolution 5mm -->1mm Halo neutron background at CC02 E391a CsI KTeV CsI

27 With Halo neutron background at E14 halo neutron / K L = 5x10-3 (E391a:0.33) low halo neutron momentum CsI resolution CC02 bkg 0.07 evts eta bkg <O(1) evts, under study

28 解 E14 Strategy 1.2 Fusion Suppress KL background 1. Identify fused photon clusters y によるもの h!! 2. Better veto, especially in the 解析して見積もる beamline C) KL!2"0 MB CsI KL γ γ γ γ BA

29 KTeV CsI Ownership is transferred from FNAL to Univ. Chicago Engineer+technician are preparing for unstacking Will start disassembling / shipping in August 2007 Will test CsI and PMTs at Osaka

30 CsI PMT base Requirements Minimize the heat and the number of vacuum feed through pedestal # of events CW base turned off h_hvon Entries Mean 1022 RMS Underflow 0 Overflow 0 Integral 4e+04 CW base turned on Low noise (<0.5mV) Studying Cockcroft-Walton base ~0.1W, low voltage DC power ADC count 4% 4 Gain change vs Rate 2 ZEUS base shows good performance Start designing CW base for KTeV tubes with Matsusada and HPK deviation (%) kHz Rate [khz] 30

31 E14 Strategy 1.2 Suppress KL background Longer CsI => suppress punch through New photon veto in the beam Beam Figure 19: Schematic side view of the BHPV arrangement.

32 Beam Hole Photon Veto Insensitive to neutrons: 2GeV/c 10-3 photon detection false hit rate : 2MHz Proven by prototype beam tests mirror 30cm Beam Pb 2mm Aerogel 5cm Winston type funnel 5 inch PMT Figure 18: Schematic view of the BHPV m the prototype (right). 31

33 KL K L->2pi0 : 3.65 K L->pi+pi-pi0 : 0.93 K L->pi e nu : 0.01 K L -> 2 gamma : negligible

34 E14 Basic Strategies 1. Suppress and control backgrounds based on the E391a experience 2. Make detector capable of handling high rates 2.1. BHPV in beam 2.2. Waveform digitization

35 E14 Strategy 2.2 Waveform digitization ~3000 (CsI) + ~1000 (others) channels Deadtime-less for 250kHz trigger 0.3MeV ~ 2GeV, 14bit, 1ns resolution and affordable Record waveform to isolate a pulse on earlier tail

36 solution = Gaussian filter + 125MHz 14bit FADC 7-poles test board Δt <0.5ns for E>10MeV Figure 10: Results of a study of two pulse separ input 1ns 10MeV test point (input) test point (shaper) power supply outp

37 Double pulse resolution Can separate >20ns apart 5:1 pulses More studies underway 200MeV + 40MeV filter 10MeV + 2MeV

38 Schedule/Priorities 1. Construct KL beamline and study it in Jan.- Feb Should understand halo neutrons 2. Build the CsI calorimeter 3. Mass production of waveform digitizer 4. Main Barrel upgrade, and close vacuum tank 5. Upgrade downstream veto 6. Upgrade upstream veto

39 Beamline Make sure that the beamline performs as designed. Should minimize radiation work. The collimator should be installed before the beam comes Neutron Neutron Density (particles/cm 2 ) x Radius at CsI (cm)

40 Schedule beamline CsI ship tests Beam survey stacking CsI comm. 1st run 2nd run Readout MainBarrel BHPV vacuum designing mass production

41 Budget Unit: 10 4 yen~$100 sum sum beamline CsI readout veto others RA,travel

42 Funding scenario Unit: 10 4 yen~$100 sum sum Tokutei US/J KEK DOE G.in Aid Amounts in yellow are allocated

43 Manpower Institution #Physicists #students technicians (+#in future) (+ #in future) & engineers (FTE) Arizona State Univ. 1 0 (+1) 0 Univ. of Chicago Chonbuk National Univ. 1 1 (+1) 0 JINR 3 2 (+2) 0 KEK Kyoto Univ. 3 4 (+4) 0 Michigan Univ. 1 (+1) 0 (+1) 1 3 NDA National Taiwan Univ. 1 2 (+1) 0.25 Osaka Univ. 2 4 (+4) 0 Pusan National Univ Saga Univ Univ. of Seoul Tbilisi State Univ. 2 0?? 0?? Yamagata Univ. 3 2 (+2) 0 Sum 31 (+1) 25 (+14) 3 6

44 Many young people

45 Institution Responsibilities Institution KEK Kyoto Osaka Yamagata Saga NDA Chicago Michigan Arizona State JINR U.Seoul, CNU Pusan Table 5: Institution responsibilities tasks Beamline, detector construction, MB upgrade Beam hole Photon and Charged vetoes, NCC2, between CsI PMT and FADC, software,... CsI & PMT test, calibration system, readout, etc., event builder Charged veto, MB upgrade, neutron counters for beam survey CC03, beamline construction CV, CC03 Readout electronics, trigger, etc. Trigger/DAQ, CsI PMT base Beamline MC, software CC04, CC05, CC06, calibration, structural analysis beam survey CV, CC03

46 We ask for a Stage 2 Approval in July Reasons Stage 2 Approval is required for starting rad certification process CsI s may not be shipped without Stage 2 Approval ( from Y.Wah) Funding request to DOE in one month needs Stage 2 Approval Postponing Stage 2 may harm foreign collaborators

47 Summary E391a is very close to opening the box Preparations for beamline and detector are going well We want to do beam survey in Feb We request a Stage 2 Approval