a sensitive probe for New Physics

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Cuthbert Lester
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1 + e branching ratio: Precise measurement of the a sensitive probe for New Physics For PiENu Collaboration A. Aguilar-Arevalo11, M. Aoki4, M. Blecher9, D.I. Britton8, D. Bryman6, S. Chen10, J. Comfort1, L. Doria5, P. Gumplinger5, C. Hurst6, A. Hussein7, Y.Igarashi3, N. Ito4, S. Kettell2, Y. Kuno4, L. Kurchaninov5, L. Littenberg2, D. Mingming10, C. Malbrunot6, T. Numao5, R. Poutissou5, A. Sher5, T. Sullivan6, D. Vavilov5, K. Yamada4, M. Yoshida3 1. Arizona State University, 2. Brookhaven National Laboratory, 3. KEK, 4. Osaka University, 5. TRIUMF, 6. University of British Columbia, 7. University of Northern British Columbia, 8. University of Glasgow, 9. Virginia Polytechnic & State Univresity, 10. Tsinghua University, 11. Instituto de Ciencia Nucleares

2 The PiENu Experiment Aim: Precision measurement of the branching ratio: The most precise SM weak interaction calculation involving quarks (<0.01%) V.Cirigliano, I.Rossell, Phys.Rev.Lett. 99, (2007) W.J.Marciano, A.Sirlin, Phys.Rev.Lett. 71, (1993) Current World Average: TRIUMF: D.A.Bryman, et al., Phys.Rev.D53: (1996) PSI: G.Czapek et al. Phys.Rev.Lett. 70: (1993) Goal: reach x5 time better precision (<0.1%) 2

Universality/New Physics search Beyond the SM extensions: Pseudo-scalar interaction <0.1% BR ep >1000 TeV Massive ν s R.E Schrock Phys.Rev.D 24, 5 (1981) Scalar coupling B.A. Campbell & David W.

3 Universality/New Physics search Beyond the SM extensions: Pseudo-scalar interaction <0.1% BR ep >1000 TeV Massive ν s R.E Schrock Phys.Rev.D 24, 5 (1981) Scalar coupling B.A. Campbell & David W. Maybury Nucl. Phys. B, (2005) <0.1% BR measurement translates to <0.05% accuracy for ge/g Compositeness N. Arkani-Hamed, S. Dimopoulos, G.R. Dvali, Phys. Lett., B429, 263 (1998) R-Parity violation SUSY M. J. Ramsey-Musolf, et al., Phys. Rev. D 76, (2007) More... 3

Experimental Technique Pions stop in the active target Both decays are registered with almost the same acceptance Calorimeter is used to discriminate decay

4 Experimental Technique Pions stop in the active target Both decays are registered with almost the same acceptance Calorimeter is used to discriminate decay modes Raw branching ratio is obtained by simultaneous fitting of two time spectra Corrections are applied the most important one is tail correction: Shower leaks 4

The PiEnu Detector Previous Experiment E248@TRIUMF Main sources of uncertainties: Low energy tail Small acceptance low statistics significant acceptance correction Silicon strips & WC around the

5 The PiEnu Detector Previous Experiment Main sources of uncertainties: Low energy tail Small acceptance low statistics significant acceptance correction Silicon strips & WC around the target + : 75MeV/c particle tracking reduce decay in flight High resolution NaI crystal close to target large solid angle (20% of 4π) Minimal energy dependence of acceptance CsI crystals ring Detects shower leakage OR Extends the NaI Calorimeter Fast digitizers 500MHz FADC for scintillators 60MHz FADC for crystals reduce pileup backgrounds 5

6 The Detector subsystems 6

7 The Detector subsystems 7

Another magnet to clean up product of interaction with

8 Beam line Beam positrons suppression Degrader after the first bending magnet Collimator after the second one Another magnet to clean up product of interaction with the collimator Beam composition π (82%) μ (14%) e+ (<2%) 8

9 The Detector performance 9

Corrections Three major source of uncertainties: Tail correction, 2

tail is measured Measuring the Calorimeter response function Statistical

corrections Suppressed spectrum analysis: Use Early Decay Time, Target

$fraction of e events left different incident angles, measure the rest is e$

10 Corrections Three major source of uncertainties: Tail correction, 2 approaches Suppressed spectrum analysis: data are used, e decay suppressed, tail is measured Measuring the Calorimeter response function Statistical 30x more statistics Better background suppression Monte Carlo Acceptance corrections Suppressed spectrum analysis: Use Early Decay Time, Target Energy, Pulse Shape Response function: Expose BINA to beam positrons in and Tracking cuts to suppress e different energy ranges and at Estimate the fraction of e events left different incident angles, measure the rest is e energy spectrum 10

11 Analysis: Heavy neutrino search (preliminary) 11

Analysis: Photonuclear effects in NaI A photon is caught by Iodine nuclei resulting to a release of a neutron Neutron escapes the calorimeter or reacts outside observation time window

12 Analysis: Photonuclear effects in NaI A photon is caught by Iodine nuclei resulting to a release of a neutron Neutron escapes the calorimeter or reacts outside observation time window More than one photoabsorption results to additional peaks 0.8% contribution to the low energy tail A.Aguilar-Arevalo et al., Nucl. Instr. and Meth. A (2010, accepted for publication) 12

Conclusion Beam Performance suppressing beam positrons was verified (clean beam) Designed stop pion rate was achieved Detector Large solid angle High resolution NaI calorimeter ScI

13 Conclusion Beam Performance suppressing beam positrons was verified (clean beam) Designed stop pion rate was achieved Detector Large solid angle High resolution NaI calorimeter ScI crystals ring to reduce shower leakage Silicon strips detectors to identify decays in flight Lower neutral pileup background due to better shielding Status Statistics of the previous experiment

The PIENU Experiment

The PIENU Experiment For the PIENU Collaboration A. Aguilar-Arevalo 11, M. Aoki 4, M. Blecher 9, D.I. Britton 8, D. Bryman 6, S. Chen 10, J. Comfort 1, L. Doria 5, P. Gumplinger 5, C. Hurst 6, A. Hussein