Дмитрий ВавиловИФВЭ 2005, 19 Декабря1 New results on rare kaon and pion...
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Transcript of Дмитрий ВавиловИФВЭ 2005, 19 Декабря1 New results on rare kaon and pion...
Дмитрий Вавилов ИФВЭ 2005, 19 Декабря 1
New results on rare kaon and New results on rare kaon and pion decays from BNL E949pion decays from BNL E949
Dmitry Vavilov
E949 is an high rate K+ decay at rest experiment with the primary goal of measuring |Vtd| via a measurement of the branching ratio of the ultra-rare charged kaon decay K++ . The report mostly concerns related limits from the decays KK++ + , KK++ + and 0 .
Дмитрий Вавилов ИФВЭ 2005, 19 Декабря 2
E949 CollaborationE949 Collaboration
USBNL, FNAL, New Mexico
CanadaTriumf, UBC, Alberta
JapanFukui, KEK, Kyoto, Osaka
RussiaIHEP, INR
Дмитрий Вавилов ИФВЭ 2005, 19 Декабря 3
E949 Detector in LESB II at BNLE949 Detector in LESB II at BNL
IHEP contributions: MC calculation for micro-Collar, Downsteam PV, RS Monitoringsystem, Slow Control, Data Analysis
Дмитрий Вавилов ИФВЭ 2005, 19 Декабря 4
E787 / E949 Data Taking SummaryE787 / E949 Data Taking Summary
Дмитрий Вавилов ИФВЭ 2005, 19 Декабря 5
KK+++ + 3d candidate event “E949A”
found
Updated branching Br(K++ ) = (1.5 +1.3
-0.9 ) x 10-10
SM predicted branching Br(K++ ) = (0.78±0.12 ) x 10-10
PNN2 analysis is in progressGoal is to reach S/N1 at comparable to PNN1 sensitivity2x Acc and 5x Rej improvements needed
E787A E787C E949A
0.006 0.02 0.07
Дмитрий Вавилов ИФВЭ 2005, 19 Декабря 6
KK++ +Introduction
Дмитрий Вавилов ИФВЭ 2005, 19 Декабря 7
KK++ +Offline AnalysisOffline Analysis
Backgrounds:K+ +0 (K2)
+ kinematics measured• Photon energies/angles mis-measured• Or photon overlaps charged track
K2 with KDecay In Flight (DIF) + Kinematics measured• Fakes K decay at rest
K+ +, 0+or K2 with DIF• + kinematics measured e decay sequence fooled
Two beam particles• Suppressed with good segmentation and
timing in the K tracking system
Дмитрий Вавилов ИФВЭ 2005, 19 Декабря 8
Backgrounds, Acceptance, SensitivityBackgrounds, Acceptance, Sensitivity
Backgrounds Number of EventsK2 0.017 ± 0.006Overlapping Photon 0.065 ± 0.065Muon 0.090 ± 0.020K decay in flight 0.025 ± 0.014Two Beam <0.006 (90%CL)
Total 0.197 ± 0.070
Дмитрий Вавилов ИФВЭ 2005, 19 Декабря 9
KK++ +KK++ +resultsBlind analyses
No events seen in signal boxes
Br(K+ + ) < 8.3 x 10-9 (90%CL)p() > 213 MeV/c
Assuming spectrum from ChPT with unitarity corrections (c = 1.8)
Factor of 8 sensitivity improvement over E787; but, cannot confirm or rule of unitarity corrections.
Same data set is used to search for K+ +which violates angular momentum conservation and gauge invariance
Br(K+ + ) < 2.3 x 10-9 (90%CL)
Factor of 160 improvement over E787
Дмитрий Вавилов ИФВЭ 2005, 19 Декабря 10
0
• Forbidden by angular momentum conservation if W’s and neutrinos are purely left handed. Can proceed if neutrinos have mass.
Br(0 ) < 1.1 x 10-9 for m()<18.2 MeV/c2
• Best previous limit comes from E787
Br(0 ) < 8.3 x 10-7 (90%CL)• Method:
Copious supply of clean 0 from K+ +0 tagged by monochromatic +.
Look for K2 events with no activity other than K+ and +.
Trigger sample is same as K+ + . Select K2 events; apply tightest photon veto.
Tune photon veto on 1/3 of data, use other 2/3 for search.
Дмитрий Вавилов ИФВЭ 2005, 19 Декабря 11
0 0 Rejection
Maxed out at ~4x106
99 events survive all cuts
Дмитрий Вавилов ИФВЭ 2005, 19 Декабря 12
0 Results
99 events remain after all photon veto cuts We presume these to be 0 with undetected photons
– The e949 photon veto inefficiency in not known and probably not knowable at this level.
– A background subtraction is not a reasonable option.
The corresponding branching ratio upper limit is:
Br(0 ) < 2.7 x 10-7 (90%CL)
Factor of 3 improvement beyond E787
Дмитрий Вавилов ИФВЭ 2005, 19 Декабря 13
ConclusionsConclusions
Present E949 resultsBr(K++ ) = (1.5 +1.3
-0.9 ) x 10-10 [3 events, E787(2) + E949(1)]
Br(K+ + ) < 8.3 x 10-9 (90%CL) p() > 213 MeV/c
Br(K+ + ) < 2.3 x 10-9 (90%CL)
Br(0 ) < 2.7 x 10-7 (90%CL)
Expected new E949 Results Br(K++ ) from region below Kp2 peak
Further Progress in ultra-rare Kaon decaysP326(Cern), Jparc(Japan)
References
K+ + Phys.Rev.Lett. 93 (2004) 031801, hep-ex/0403036
K+ +K+ +T. Yoshioka, Univ. of Tokyo thesis, KEK K-decay Report 2005-2, Hep-ex/0505069, Phys.Lett.B 623 (2005) 192-199
0 K.Mizouchi, Kyoto Uinv. Thesis (in preparation), hep-ex/0506028, submitted to Phys.Rev.D. Rapid Communications
Дмитрий Вавилов ИФВЭ 2005, 19 Декабря 14
KK++ +in Chiral Perturbation Theory