Status of the MEG Experiment m → e g

Status of the MEG Experiment m→ e g On behalf of the MEG collaboration Stefan Ritt Paul Scherrer Institute, Switzerland

LVF in the charged sector Quarks Quark mixing (CKM) t c b s u t Mixing in the charged Lepton sector? d m e Energy Leptons n t n m Neutrino Oscillations n e • 2 3 • Generation

LFV in the SM vs. SUSY probes slepton mixing matrix SM SUSY ≈ 10-12 • LFV in the SM is immeasurable small • SUSY models predicts BR(m → eg) just below the current experimental limit of 1.2 x 10-11 • Decay m → eg is free of “SM background” (no hadronic corrections) The discovery of m → e g would by physics beyond the SM

m→ e g “Supersymmetric parameterspace accessible by LHC” mA→ eA m→ eee MEG W. Buchmueller, DESY, priv. comm. Summary of LFV experiments 10-1 SUSY SU(5) BR(m e g) = 10-13 mA  eA = 10-15BR(tmg) = 10-8 10-2 10-3 10-4 10-5 10-6 10-7 10-6 BR 10-9 10-10 10-11 10-12 10-13 Current Limits: BR(m+ e+g) < 1.2 x 10-11 (MEGA)1) mTi → eTi < 7 x 10-13 (SINDRUM II)2) 10-14 10-15 1940 1950 1960 1970 1980 1990 2000 2010 Year 1) hep-ex/9905013 2) A. van der Schaaf, priv. comm.

m – e Conversion: Sindrum II @ PSI Bme=4 •10-12 m-Ti  e-Ti : 4.3 x 10-12 (90% C.L.) m-Au → e-Au : <7 x 10-13 (90% C.L.) Limited by p decay in flight

PRISM/PRIME at J-PARC 1011 – 1012m/sec pulsed beam p/m < 10-18 Magnet construction -2008 Terminated in August 2005 m – e Conversion down to 10-18 m – e Conversion: Future RSVP program at BNL m – e Conversion down to 10-17

Univ. of Tokyo Y. Hisamatsu, T. Iwamoto, T. Mashimo, S. Mihara, T. Mori, Y. Morita, H. Natori, H. Nishiguchi, Y. Nishimura, W. Ootani, K. Ozone, R. Sawada, Y. Uchiyama, S. Yamashita KEK T. Haruyama, K. Kasami, A. Maki, Y. Makida, A. Yamamoto, K. Yoshimura Waseda Univ. K. Deguchi, T. Doke, J. Kikuchi, S. Suzuki, K. Terasawa INFN Pisa A. Baldini, C. Bemporad, F. Cei, L.del Frate, L. Galli, G. Gallucci, M. Grassi, F. Morsani, D. Nicolò, A. Papa, R. Pazzi, F. Raffaelli, F. Sergiampietri, G. Signorelli INFN and Univ. of Genova S. Cuneo, D. Bondi, S. Dussoni, F. Gatti, S. Minutoli, P. Musico, P. Ottonello, R. Valle INFN and Univ. of Pavia O.Barnaba, G. Boca, P. W. Cattaneo, G. Cecchet, A. De Bari, P. Liguori, G. Musitelli, R. Nardò, M. Rossella, A.Vicini INFN and Univ. of Roma I A. Barchiesi, D. Zanello INFN and Univ. of Lecce M. Panareo Paul Scherrer Institute J. Egger, M. Hildebrandt, P.-R. Kettle, S. Ritt, M. Schneebeli BINP Novosibirsk L. M. Barkov, A. A. Grebenuk, D. N. Grigoriev, B. I. Khazin, N. M. Ryskulov JINR Dubna A. Korenchenko, N. Kravchuk, A. Moiseenko, D. Mzavia Univ. of California, Irvine W. Molzon, M. Hebert, P. Huwe, J. Perry, V. Tumakov, F. Xiao, S. Yamada MEG S ~40 FTEs

g g n m n n n m e e Decay topology Main background m e g g m  e nn g m Annihilation in flight 180º e m  e nn g • m→ e g signal very clean • Eg = Ee = 52.8 MeV • qge = 180º • e and g in time Good energy resolution Good spatial resolution Excellent timing resolution Good pile-up rejection

The MEG Detector • 107 – 108m/sec, 100% duty factor • LXe for efficient g detection • Solenoidal magnetic spectrometer

Detector parts LXe calorimeter prototype “COBRA” solenoid Timing counter

Drift chamber for positrons

Experimental set-up pE5 beamline Detailed studies to minimize background from annihilation in flight Currently the highest intensity m beam: 108m/sec. m

Pile-up rejection with the DRS chip 11 MeV g + 42 MeV g DT=15ns • 4 GHz sampling rate @ 12 bits • 32 channels on VME board • ~ 100 € per channel • Licensed to CAEN, Italy Only use waveform Digitizing for the whole experiment~3000 channels (no ADC, TDC, …) a source g shower

http://meg.web.psi.ch/docs/calculator/ Current sensitivity estimation Subject to future improvements

1999 R&D 2000 2001 2002 2003 2004 2005 2006 Engineering 2007 Data 2008 2009 • Plans • Data taking from 2007 on to reach 10-13 sensitivity (90% CL) • Obtain a “significant” result before the LHC era • Eventual reach10-14 during LHC era

Status of the MEG Experiment m → e g