Measuring K+ → π
+νν with NA48/3
Rainer Wanke
Institut fur Physik, Universitat Mainz
on behalf of
CERN, Dubna, Ferrara, Florence, Frascati, Mainz, Merced, Moscow, Naples,
Perugia, Pisa, Protvino, Rome, Saclay, Sofia, Torino
K-RARE Meeting
Frascati, May 26, 2005
Rainer Wanke, K-RARE Meeting, Frascati, May 26, 2005 – p.1/25
Outline
Introduction
K+ Beam
Detector Design
Time Schedule
Summary and Conclusion
Nota bene:
Exp. historically dubbed NA48/3, but not direct successor of NA48/2!Mainly new detectors, and will get new name when approved.
Correct name at the moment: P326 (Proposal no. 326)
Rainer Wanke, K-RARE Meeting, Frascati, May 26, 2005 – p.2/25
The Opportunity
Expected SPS Performance for Fixed-Target: (R. Garoby, Villars 2004)
=⇒ ≥ 3 × 105 proton spills per year for fixed-target.
Rainer Wanke, K-RARE Meeting, Frascati, May 26, 2005 – p.3/25
High Intensity K+ Beam
Parameters of the high intensity K+ beam:
K12 in 2004 HI-K+ ≥ 2007(NA48/2) (NA48/3)
Eff. run time/year (pulses) 3 × 105 3 × 105
SPS protons/pulse 1 × 1012 3 × 1012
K+ momentum 60.0 ± 2.5 GeV/c 75.0 ± 0.8 GeV/c
Acceptance solid angle 0.4 µsterad 16 µsterad
Total beam flux/pulse 5.5 × 107 250 × 107
kaons/pulse 0.3 × 107 15 × 107
K+ decays/year 1.0 × 1011 4.8 × 1012
Rainer Wanke, K-RARE Meeting, Frascati, May 26, 2005 – p.4/25
K+ → π
+νν at the CERN SPS
NA48/3:
4.8 × 1012 K+ decays/year
Br(K+ → π+νν) ∼ 10−10
Acceptance ∼ 10%
Dead time ∼ 20%
=⇒ About 80 K+ → π+νν
events in 2009/10.
Background:
K+ → π+π0 (Br ≈ 0.2),K+ → µ+ν (Br ≈ 0.6)
=⇒ Photon/muon vetos,exact momentum meas.
Signal/Background ≈ 10.
θπKPK
Pπ
Pν
Pν
Pπ (GeV/c)
θπK PK = 75 GeV/c
Kµ2
K+ π+νν−
K+ ππ0
K+ π+π0π0
K+ π+π+π−
0
0.002
0.004
0.006
0.008
0.01
0.012
0.014
0.016
0.018
0.02
0 10 20 30 40 50 60 70
Region 1
Region 2
Rainer Wanke, K-RARE Meeting, Frascati, May 26, 2005 – p.5/25
Acceptance
Two regions for measuring K+ → π+νν:
Region 1: 0 < m2miss < 0.01 GeV2/c4 =⇒ Acc ≈ 4.5 %
Region 2: 0.026 < m2miss < 0.068 GeV2/c4 =⇒ Acc ≈ 14.5 %
(Both with 15 < pπ < 35 GeV/c, no analysis cuts, no dead time yet)
-0.15 -0.1 -0.05 0 0.05 0.1 0.154/c2 GeVmiss
2m
Arb
itra
ry U
nit
s
0π+π→+K
ν+µ
→+K
-π+π+π→+K
νν+π→+K
Reg
ion
I
Region II
m2miss = (pK − pπ)2 = m2
K + m2π − 2 EK Eπ + 2 ~pK ~pπ cos θKπ
Rainer Wanke, K-RARE Meeting, Frascati, May 26, 2005 – p.6/25
In 2010?
(Standard model)100 events
100 events(E949 value)
(3 events)Now:
?
Rainer Wanke, K-RARE Meeting, Frascati, May 26, 2005 – p.7/25
Backgrounds for K+ → π
+νν
Decay B.R. [%] Type of rejection
K+ → µ+ν (Kµ2) 63 µ particle ID, kinematicsK+ → µ+νγ (Kµ2γ ) 0.55 µ particle ID, photon vetoK+ → π+π0
21 photon veto, kinematicsK+ → π+π+π−
6 charged veto, kinematicsK+ → π0π0π+
2 photon veto, kinematicsK+ → π0µ+ν (Kµ3) 3 photon veto, µ particle IDK+ → π0e+ν (Ke3) 5 photon veto, E/p
-0.15 -0.1 -0.05 0 0.05 0.1 0.154/c2 GeVmiss
2m
Arb
itra
ry U
nit
s
0π+π→+K
ν+µ
→+K
-π+π+π→+K
νν+π→+K
Reg
ion
I
Region II
Rainer Wanke, K-RARE Meeting, Frascati, May 26, 2005 – p.8/25
Detector Design
Detector design follows from need for maximum background rejection:
Precise knowledge of K+ momentum for m2miss determination.
=⇒ Gigatracker — K+ beam spectrometer
Photon rejection.
=⇒ Photon-Vetos — LAV, Lkr, SAC
Precise π+ momentum measurement to reject two-body decays
=⇒ Straw Tracker — double magnetic spectrometer
Optimal π+/µ+ separation for K+ → µ+ν rejection
=⇒ Muon Detector, RICH
K+–π+ matching
=⇒ CEDAR in K+ beam, Hodoscope for charged particles
Rainer Wanke, K-RARE Meeting, Frascati, May 26, 2005 – p.9/25
Detector Layout
VACUUM
CEDAR
LKr
ANTIANTI
ANTI
IRC
1,2
SAC
Target
200 240
Z (m)
0 100
1 m
Ne
1 atm
C1 C2TAX
CHOD
M1 M2
Final Coll.
MAMUDRICH
FTPC
Achromat 1
SPIBES1,2C3
Achromat 2
Straw Tubes
10 MHzKaon decays
800 MHzK, pi, mu
Rainer Wanke, K-RARE Meeting, Frascati, May 26, 2005 – p.10/25
CEDAR — K+ Identification
Requirement: K+/π+ separation in charged particle beam.
=⇒ CEDAR Differential Cerenkov Counter
CEDAR counters have been in use in SPS beams.(Two versions: He-filled “North-CEDAR”, N2-filled “West-CEDAR”.)
West-CEDAR, filled with hydrogen, perfect for NA48/3 application.
Beam
Mirror
Light path
CorrectorRing ImagePMs
Rainer Wanke, K-RARE Meeting, Frascati, May 26, 2005 – p.11/25
Gigatracker — K+ Momentum
Requirements:K+ momentum resolution ∼ 0.3%.
Angular resolution ∼ 10 µrad.
Time resolution ∼ 150 ps per station.
Material budget ≤ 0.5 X0 per station.
Survive 1 GHz hadron beam (60 MHz/cm2).
Design: Hybrid detector
SPIBES (Fast Si micro-pixels)
Momentum and time measurement.2 stations of hybrid silicon pixel detectors.
FTPC
Angular measurement (track direction).Micromegas TPC’s as in NA48/2 (but with FADC read-out).
=⇒ See presentation by M. Scarpa tomorrow!Rainer Wanke, K-RARE Meeting, Frascati, May 26, 2005 – p.12/25
Photon Vetos
Requirement:
Suppression of K+ → π+π0, K+µ3, K+ → π+γγ, . . .
=⇒ Inefficiency ≤ 10−4 for Eγ > 100 MeV (and ≤ 10−5 for Eγ > 1 GeV).
Components:
Large Angle Vetos (ANTI)
Lead-scintillator sandwich calorimeter around decay region.
Liquid-Krypton Calorimeter (LKr)
Use existing NA48 calorimeter.
Small Angle Vetos (IRC, SAC)
Covering of the beam pipe, lead-scintillator sandwich.
Rainer Wanke, K-RARE Meeting, Frascati, May 26, 2005 – p.13/25
Large Angle Photon Vetos (ANTI)
Coverage: > 8.5 mrad (LKr calorimeter)
< 50 mrad (kinematical limit for γ’s from K+ → π+π0)
=⇒ 13 veto counters around decay region.
Rainer Wanke, K-RARE Meeting, Frascati, May 26, 2005 – p.14/25
Large Angle Photon Vetos (ANTI)
Design of each veto counter:
80 layers lead-scintillator sandwich, each 16 X0 deep.
Arrangement in segmented rings inside vacuum tank.
Read-out by WLS fibers.
=⇒ ∼ 20 photo electrons/minimum ionizing particle.
Alternative design:
Lead with embeddedscintillator(“spaghetti calorimeter”).
Better time, energyresolution.
Currently investigated.
Rainer Wanke, K-RARE Meeting, Frascati, May 26, 2005 – p.15/25
Liquid-Krypton Calorimeter
Main detector element forNA48/0/1/2.
13212 cells of 2 × 2 cm2 alongbeam axis in ∼ 10 m3 liquidkrypton.
Very good energy resolution(3.2%/
√
E [GeV])
Noise about 90 MeV.
Veto capabilities to be verified.
Few upgrades necessary(Read-out, kryogenic system).
Rainer Wanke, K-RARE Meeting, Frascati, May 26, 2005 – p.16/25
Small Angle Photon Vetos
Detectors:
IRC: Coverage of beam pipe inside calorimeters.
SAC: Coverage down to θ = 0.
SAC
beam
LKr
IRC
RICH
CHOD
MAMUD
Design: Two possibilities considered:
Shashlik technique.Layers of Pb + scintillator (total ≈ 17 X0)
PbWO4 crystals.
Rainer Wanke, K-RARE Meeting, Frascati, May 26, 2005 – p.17/25
Magnetic Spectrometer
Requirements:
Suppress K+ → µ+ν by 10−8 =⇒ Exact momentum measurement
Minimum material =⇒ Minimum of multiple scattering.
Redundancy =⇒ Suppression of non-gaussian errors.
=⇒ Design: Double spectrometer, operation in vacuum.
Z
MNP33(1)
10 m 7 m 7 m
2.3 m
5 m 5 m
from the target
205 m
MNP33(2)
VUX YX Y U VVUYXX Y VUX Y U V X Y U V
Rainer Wanke, K-RARE Meeting, Frascati, May 26, 2005 – p.18/25
Magnetic Spectrometer
Chamber design: Straw chambersLayer 2
Layer 1
Pion track
Operation in vacuum possible.
Well-known technology (ATLAS TRT, COMPASS).
Experience available (JINR, Dubna).
18 cm
X(Y)
X(Y)
X(Y)
U(V)
U(V)
U
U
Y
X
U(V
)
230 cm
Compass
Rainer Wanke, K-RARE Meeting, Frascati, May 26, 2005 – p.19/25
MAMUD — Magnetized Muonand hadron Detector
Requirements:
π/µ separation for Kµ2 suppression
Beam sweeping for SAC operation.
Design:
Magnetised iron =⇒ 0.9 T field in beam region.
Instrumented by scintillators =⇒ muon rejection ∼ 105.
sum(Emax)/sum(E)
K+ → πνν
K+ → µν (x4)
Rainer Wanke, K-RARE Meeting, Frascati, May 26, 2005 – p.20/25
Charged Hodoscope, RICH
Charged Hodoscope (CHOD)
Excellent time resolution < 100 ps.
Rejection of high-multiplicity events (K+ → π+π+π−, . . . ).
Trigger (together with photon vetos and CEDAR).
Design: Multigap glass RPC, similar to ALICE TOF.
RICH
Needed for additional Kµ2, Kµ2γ rejection.(π/µ seperation at 2 sigma level is sufficent.)
Design currently under investigation (e.g. KPLUS design).
Rainer Wanke, K-RARE Meeting, Frascati, May 26, 2005 – p.21/25
Expected Background
Decay B.R. [%] Bkg. Estim.
K+ → µ+ν (Kµ2) 63.4 ∼ 1.6
K+ → µ+νγ (Kµ2γ) 0.6 ∼ 0.4
K+ → π+π0 21.1 ∼ 4.4
K+ → π+π0γ 0.03 < 0.1
K+ → π0e+ν (Ke3) 4.9 ∼ 1.6
K+ → π0µ+ν (Kµ3) 3.3 < 0.1
K+ → π+π+π− 5.6 in progress
Total: ∼ 8 (+ 3-track)
=⇒ See presentation by G. Ruggiero this afternoon!
Rainer Wanke, K-RARE Meeting, Frascati, May 26, 2005 – p.22/25
Timeline
2005:
Proposal to the SPSC — being submitted.(CERN-SPSC-2005-013)
Design and Development of main detector components.(Beam spectrometer, magnet spectrometer, photon vetos,muon detector, RICH)
2006 – 2008:
Building, tests and installation of detector components.( =⇒ SPS test-beam in 2006.)
2009/2010:
Beam time at the CERN SPS.
Til 2011/2012: Data analysis.
Rainer Wanke, K-RARE Meeting, Frascati, May 26, 2005 – p.23/25
CERN Recommendation for NA48/3
From the Villars report (CERN-SPSC-2005-010, Feb 28, 2005):
=⇒ Formally invited by the SPSC to submit a proposal.
Rainer Wanke, K-RARE Meeting, Frascati, May 26, 2005 – p.24/25
Summary and Conclusion
NA48/3: Impressive opportunity to measure
≥ 80 K+ → π+νν events in 2009/2010 at the CERN SPS.
Backgrounds are challenging, but under control!
Expect: Signal/background ≈ 10.(Even better when using RICH detector!)
NA48/3 detector currently developped.
Main components: Beam spectrometer, photon vetos,straw tracker, muon rejection.
Rely if possible on well-known technology.Reuse of few components (Lkr) from old NA48.
Proposal written, signed by about 80 physicists.
We are still open to new collaborators.
Rainer Wanke, K-RARE Meeting, Frascati, May 26, 2005 – p.25/25