A personal overview of particle physics activities at PSI

1November 16th 2007

A personal overview of particle physics activities at

PSI

A. M. BaldiniINFN Pisa

2November 16th 2007

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

3November 16th 2007

Two graphite targets M (mm), E(cm) from which several secondary beams are extractedNamed as or – E or M - #

e.g.: E3

70% of the beam is sent to SINQ, a neutron spallation source for materials studies, solid state physics...

Roughly 107 /s

4November 16th 2007

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: r contains all

relevant loop corrections: GF current precision constitutes a

limit to these fits

5November 16th 2007

MuLan at E3

• Surface muons (28.8 MeV/c) coming from 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

6November 16th 2007

FAST

Use of a pion beam (M1): 170 MeV/c @ 1 MHzArray of plastic scintillating fibers read by multi-anode PMTsNo polarization problems

In principle should reach a 1 ppm GF measurement but it is having several problems with electronics

t < 1ppm in future?Radiative corrections would support another order of magnitude on t (beyond 1 ppm) but that would go way beyond the precision of the other electroweak parameters

7November 16th 2007

Another tradition: LFV searches by using muons: + e+ search

Lab. Year Upper limit Experiment or Auth.

PSI 1977 < 1.0 10-9 A. Van der Schaaf et al.

TRIUMF 1977 < 3.6 10-9 P. Depommier et al.

LANL 1979 < 1.7 10-10 W.W. Kinnison et al.

LANL 1986 < 4.9 10-11 Crystal Box

LANL 1999 < 1.2 10-11 MEGA

PSI ~2010 ~ 10-13 MEG

Two orders of magnitude improvement

several SUSY GUT and SUSY see-saw models predict BRs at the reach of

MEG

8November 16th 2007

SUGRA indications

• SUSY SU(5) predictions

BR (e) 10-14 10-13

• SUSY SO(10) predictionsBRSO(10) 100 BRSU(5)

R. Barbieri et al., Phys. Lett. B338(1994) 212R. Barbieri et al., Nucl. Phys. B445(1995) 215

LFV induced by slepton mixing

MEG goal

Experimental limit (MEGA)

combined LEP results favour tan>10

9November 16th 2007

Our goal

Experimental limit

Connection with -oscillations

J. Hisano, N. Nomura, Phys. Rev. D59 (1999)

Additional contribution to slepton mixing from V21 (the matrix element responsible for solar neutrino deficit)

tan()=30

tan()=1

After SNO After Kamland

-5410R in the Standard Model !!

10November 16th 2007

Signal and background

e+ +

e = 180°Ee = E = 52.8 MeVTe = T

signal e

background

physical e

e+ +

accidental

e e

ee eZ eZ e+ +


The sensitivity is limited by the accidental background

2phys.b. RnRnRn μacc.b.μμsig , ,

2eγeγ ΔΔ θt 2

γe ΔΔ EE accBR

Integral on the detector resolutions of the Michel and radiative decay spectra

Effective BRback (nback/R)

The n. of acc. backg events (nacc.b.) depends quadratically on the muon rate and on how well we measure the experimental

quantities: e- relative timing and angle, positron and photon energy

μR


Required Performances

Exp./Lab Year Ee/Ee

(%)

E/E

(%)

te (ns)

e

(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 1977 10 8.7 6.7 - 2 x 105 100 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 8 8 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 107 100 1 x 10-13

FWHM

BRacc.b. 2 10-14 and BRphys.b. 0.1 BRacc.b. with the following resolutions

Need of a DC muon beam

BR (e) 10-13 reachable


Experimental method

1m

e+

Liq . Xe Scin tilla tionDetector

Drift Cham ber

Liq. Xe Scintilla tionDetector

e+

Tim ing Counter

Stopping TargetThin Superconducting Co il

M uon Beam

Drift Cham ber

Detector outline1. Stopped beam of 3 107

/sec in a 150 m target2. Solenoid spectrometer &

drift chambers for e+ momentum

3. Scintillation counters for e+ timing

4. Liquid Xenon calorimeter for detection (scintillation)- fast: 4 / 22 / 45 ns- high LY: ~ 0.8 * NaI- short X0: 2.77 cm


The PSI E5 DC beam

Primary proton beam

•28.8 MeV/c muons from decay of stop at rest: fully polarized

+

Particles intensity as a function of the selected momentum

108 /s could be stopped in the target but only 3x107 will be used because of accidental background

E target


A new kind of calorimeter: experimentally measured resolutions

4.8 % FWHM4.8 % FWHM

FWHMT) 150 ps

- p 0 n e 0

x= 2 - 4 mm

LED

PMT Gain

Higher V with light att.

Can be repeated frequently

alpha

PMT QE & Att. L

Cold GXe

LXe

Laser

Laser

(rough) relative timing calib.

< 2~3 nsec

Nickel Generator 9 MeV Nickel γ-line

NaI

Polyethylene

0.25 cm Nickel plate

3 cm 20 cm

quelle

onoff

Illuminate Xe from the back

Source (Cf) transferred by comp air on/off

Proton Acc Li(p,)Be

LiF target at COBRA center

17.6MeV

~daily calib.

Can be used also for initial setup

KBi

TlF

Li(p, 0) at 17.6 MeV

Li(p, 1) at 14.6 MeV

radiative decay

0 - + p 0 + n

0 (55MeV, 83MeV)

- + p + n (129MeV)

10 days to scan all volume precisely

(faster scan possible with less points)

LH2 target

e+

e-

e

Lower beam intensity < 107

Is necessary to reduce pile-ups

Better t, makes it possible to take data with higher beam intensity

A few days ~ 1 week to get enough statistics

XenonCalibration

MEG status report

18


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 e (BR 10-13) and possibly below…

1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010

Planning R & D Assembly Data Taking

nownowLoILoI ProposalProposal

RevisedReviseddocumentdocument


The future of LFV searches with muons

Decay In Orbit

• Accidental background: e sensitivity not much below the MEG one. Maybe 10-14÷15 possible• 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


Beam related background

Moderator: range about ½ range

• 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

SINDRUM


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


edm: a possibility for the future at PSI•Theoretically related to e • 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 edm (A. Adelmann and K. Kirch, hep-ex/0606034)

p = 125 MeV/c , P ≈ 0.9 at E1 beam line

= 1.57B = 1 TE = 0.64 MV/mR = 0.36 m

in one year of running

A table-top experiment

• 4 orders of magnitude improvement

cm e105 23 d


Muon EDM Limits

S. Eidelman et al., PLB 592(2004)1

SM : < 10-36

Proof of the measurement principle to judge about the realization of much larger experiment


Thank you and many apologies for not having been able to come to Fermilab

A personal overview of particle physics activities at PSI

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