# Presentation: 885239

## 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

- 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  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

## 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

##  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

## FAST

- Use of a pion beam (M1): 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

** ********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**

## 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

## SUGRA indications

- SUSY SU(5) predictions
- BR (e)  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

- LFV induced by  slepton mixing

- combined LEP results favour tan>10

## Connection with -oscillations

- 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**

- in the Standard Model !!

## Signal and background

- e = 180°
- Ee = E = 52.8 MeV
- Te = T

- signal
-   e 

- background

- physical
-   e 

- accidental
-   e
-   e 
- ee  
- eZ  eZ

- 	

## The sensitivity is limited by the accidental background

- 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

## 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

- Detector outline
- Stopped beam of 3 107  /sec in a 150 m 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

## The PSI E5 DC beam

- The PSI E5 DC 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

## Slide 15

## A new kind of calorimeter: experimentally measured resolutions

_**4.8 % FWHM**_
- FWHMT)  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

**(rough) relative timing calib.**
**< 2~3 nsec**

- Nickel  Generator

**9 MeV**** Nickel**** γ-line**

- NaI

***Polyethylene***

***0.25 cm Nickel plate***

**quelle**

- on

- off

**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**
****

- K

- Bi

- Tl

- F

- 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)**
**LH****2**** target**

****

**e****+**

**e****-**

**e**

****

****

****

****

**Lower beam intensity < 10****7**
**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**

- Xenon
- Calibration

## 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

**now**

**LoI**

**Proposal**

**Revised**
**document**

## 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 1⁄2 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
- = 1.57
- B = 1 T
- E = 0.64 MV/m
- R = 0.36 m

- in one year of running

- A table-top experiment

-  4 orders of magnitude improvement

## 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

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

## Slide 28