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A personal overview of particle physics activities at PSI

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 (1.8 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.: p E3.

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A personal overview of particle physics activities at PSI

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

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

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

  4. PSI has a tradition on precision measurements. Muon lifetime: MuLan and Fast In V-A theory muon lifetime factorizes intoa weak contribution plusradiative 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

  5. 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

  6. 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

  7. Another tradition: LFV searches by using muons: m+  e+g search Two orders of magnitude improvement several SUSY GUT and SUSY see-saw models predict BRs at the reach of MEG

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

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

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

  11. The sensitivity is limited by theaccidental 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

  12. 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 Need of a DC muon beam

  13. Experimental method • Detector outline • Stopped beam of 3 107 /sec in a 150 mm target • Solenoid spectrometer & drift chambers fore+ 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

  14. Primary proton beam The PSI pE5 DC 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 108m/s could be stopped in the target but only 3x107 will be used because of accidental background

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

  16. m radiative decay Laser 20 cm 3 cm LED Laser 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 g e m (rough) relative timing calib. < 2~3 nsec n n 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 Nickelγ-line on off quelle K Bi NaI Illuminate Xe from the back Source (Cf) transferred by comp air  on/off Tl Li(p, 1) at 14.6 MeV F Polyethylene 0.25 cm Nickel plate Li(p, 0) at 17.6 MeV

  17. 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

  18. 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

  19. 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

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

  21. 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

  22. 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)

  23. 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 PSI m edm (A. Adelmann and K. Kirch, hep-ex/0606034) A table-top experiment in one year of running • 4 orders of magnitude improvement

  24. 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

  25. Thank you andmany apologies for not having been able to come to Fermilab

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