A personal overview of particle physics activities at PSI A. M. Baldini INFN Pisa

Currently 2 mA (1. 2 MW) will be increased to 3 (1 Currently 2 mA (1.2 MW) will be increased to 3 (1.8 MW) in the near future

Two graphite targets M (mm), E(cm) from which several secondary beams are extracted Named as p or m – E or M - # e.g.: pE3 Roughly 107 m/s 70% of the beam is sent to SINQ, a neutron spallation source for materials studies, solid state physics...

e.g.Mass limits for Higgs Search PSI has a tradition on precision measurements. Muon lifetime: MuLan and Fast In V-A theory muon lifetime factorizes into a weak contribution plus radiative corrections. e.g.Mass limits for Higgs Search The Fermi constant is an input to all precision electroweak studies: Dr contains all relevant loop corrections: GF current precision constitutes a limit to these fits

MuLan at pE3 Surface muons (28.8 MeV/c) coming from p decay at rest on the surface of the E target Scintillator tiles + PMTs arranged symmetrically to reduce unwanted muon polarization effects Beam structure created artificially 20 muons of the DC beam are used every 10 muon lifetimes 1012 events collection: final 1 ppm measurement : improvement of one order of magnitude wrt previous measurements Recent (2007) result: 11 ppm measurent (almost a factor 2 improvement): paper submitted to PRL

Dtm < 1ppm in future? FAST Use of a pion beam (pM1): 170 MeV/c @ 1 MHz Array of plastic scintillating fibers read by multi-anode PMTs No polarization problems In principle should reach a 1 ppm GF measurement but it is having several problems with electronics Dtm < 1ppm in future? Radiative corrections would support another order of magnitude on tm (beyond 1 ppm) but that would go way beyond the precision of the other electroweak parameters

Another tradition: LFV searches by using muons: m+  e+ g search Lab. Year Upper limit Experiment or Auth. PSI 1977 < 1.0  10-9 A. Van der Schaaf et al. TRIUMF < 3.6  10-9 P. Depommier et al. LANL 1979 < 1.7  10-10 W.W. Kinnison et al. 1986 < 4.9  10-11 Crystal Box 1999 < 1.2  10-11 MEGA ~2010 ~ 10-13 MEG Two orders of magnitude improvement several SUSY GUT and SUSY see-saw models predict BRs at the reach of MEG

SUSY SU(5) predictions BR (meg)  10-14  10-13 SUGRA indications LFV induced by slepton mixing MEG goal Experimental limit (MEGA) SUSY SU(5) predictions BR (meg)  10-14  10-13 SUSY SO(10) predictions BRSO(10)  100 BRSU(5) R. Barbieri et al., Phys. Lett. B338(1994) 212 R. Barbieri et al., Nucl. Phys. B445(1995) 215 combined LEP results favour tanb>10

Connection with n-oscillations Additional contribution to slepton mixing from V21 (the matrix element responsible for solar neutrino deficit) J. Hisano, N. Nomura, Phys. Rev. D59 (1999) Our goal Experimental limit tan(b)=30 tan(b)=1 After SNO After Kamland in the Standard Model !!

background signal   e g accidental   e n n   e g n n ee  g g Signal and background background signal   e g accidental   e n n   e g n n ee  g g eZ  eZ g physical   e g n n e+ + g e+ + g n e+ + n qeg = 180° Ee = Eg = 52.8 MeV Te = Tg g

The sensitivity is limited by the accidental background The n. of acc. backg events (nacc.b.) depends quadratically on the muon rate and on how well we measure the experimental quantities: e-g relative timing and angle, positron and photon energy Effective BRback (nback/Rm T) Integral on the detector resolutions of the Michel and radiative decay spectra

Required Performances BR (meg)  10-13 reachable BRacc.b.  2 10-14 and BRphys.b.  0.1 BRacc.b. with the following resolutions FWHM Exp./Lab Year DEe/Ee (%) DEg /Eg Dteg (ns) Dqeg (mrad) Stop rate (s-1) Duty cyc.(%) BR (90% CL) SIN 1977 8.7 9.3 1.4 - 5 x 105 100 3.6 x 10-9 TRIUMF 10 6.7 2 x 105 1 x 10-9 LANL 1979 8.8 8 1.9 37 2.4 x 105 6.4 1.7 x 10-10 Crystal Box 1986 1.3 87 4 x 105 (6..9) 4.9 x 10-11 MEGA 1999 1.2 4.5 1.6 17 2.5 x 108 (6..7) 1.2 x 10-11 MEG 2009 0.8 4 0.15 19 2.5 x 107 1 x 10-13 Need of a DC muon beam

Detector outline Experimental method Stopped beam of 3 107  /sec in a 150 mm target Solenoid spectrometer & drift chambers for e+ momentum Scintillation counters for e+ timing Liquid Xenon calorimeter for  detection (scintillation) fast: 4 / 22 / 45 ns high LY: ~ 0.8 * NaI short X0: 2.77 cm

Particles intensity as a function of the selected momentum The PSI pE5 DC beam Primary proton beam E target Particles intensity as a function of the selected momentum m+ 28.8 MeV/c muons from decay of  stop at rest: fully polarized 108 m/s could be stopped in the target but only 3x107 will be used because of accidental background

A new kind of calorimeter: experimentally measured resolutions  - p  0 n e 0    4.8 % FWHM FWHM(T)  150 ps x= 2 - 4 mm

m radiative decay Laser LED g e m n n p0 gg alpha Nickel g Generator Lower beam intensity < 107 Is necessary to reduce pile-ups Better st, makes it possible to take data with higher beam intensity A few days ~ 1 week to get enough statistics e m n n (rough) relative timing calib. < 2~3 nsec Laser PMT Gain Higher V with light att. Can be repeated frequently p0 gg p- + p  p0 + n p0  gg (55MeV, 83MeV) p- + p  g + n (129MeV) 10 days to scan all volume precisely (faster scan possible with less points) LH2 target alpha Xenon Calibration PMT QE & Att. L Cold GXe LXe e+ g e- Nickel g Generator Proton Acc Li(p,)Be LiF target at COBRA center 17.6MeV g ~daily calib. Can be used also for initial setup 9 MeV Nickel γ-line on off 3 cm 20 cm quelle K Bi NaI Tl Illuminate Xe from the back Source (Cf) transferred by comp air  on/off F Li(p, 1) at 14.6 MeV Polyethylene Li(p, 0) at 17.6 MeV 0.25 cm Nickel plate

MEG time scale Detectors commissioning going on: soon start of data taking Goal: hope to get a significant result before entering the LHC era Measurements and detector simulation make us confident that we can reach the SES of 4 x 10-14 to meg (BR 10-13) and possibly below… Revised document now LoI Proposal Planning R & D Assembly Data Taking 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010

The future of LFV searches with muons Accidental background: meg sensitivity not much below the MEG one. Maybe 10-14÷15 possible me conversion in nuclei does not have this problem: single e+ sign. Best present sensitivity achieved by SINDRUM II at PSI: <7 10-13 @ 90% C.L.: W. Bertl et al., EPJ C47(2006) 37  Decay In Orbit

Beam related background Moderator: range  about ½ range  SINDRUM At higher muon rates ( 1011 /s) a good strategy (ex MECO) would be to use a pulsed proton beam and make measurements in a time window distant from the beam pulse This will not be possible at PSI

An important project for PSI: the spallation Ultra Cold Neutron source

n EDM: P and T violating 1. At the UCN facility at the ILL (Grenoble) reactor 2. Move the spectrometer to PSI 2. Project, build and operate a new spectrometer (n2EDM) ay PSI later on

m edm: a possibility for the future at PSI Theoretically related to m e g Disentangle the EDM effect from the g-2 precession by means of a radial electric field: JPARC LOI (Jan 2003) for a dedicated experiment->10-24 e.cm level M. Aoki et al. + F.J.M. Farley et al., PRL 93 0521001(2004) g-2 precession cancelled. Only the one related to the electric dipole moment, out of the storage ring plane, left: up-down detectors measure the asymmetry build up with time High intensity beam of 0.5 GeV/c polarized muons (JPARC LOI)

PSI m edm (A. Adelmann and K. Kirch, hep-ex/0606034) pm = 125 MeV/c , P ≈ 0.9 at mE1 beam line = 1.57 B = 1 T E = 0.64 MV/m R = 0.36 m A table-top experiment in one year of running 4 orders of magnitude improvement

Muon EDM Limits S. Eidelman et al., PLB 592(2004)1 Proof of the measurement principle to judge about the realization of much larger experiment SM : < 10-36

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