P and T violating correlation in muon and beta decays

P and T violating correlationin muon and beta decays

Oscar Naviliat-CuncicLPC-Caen (IN2P3/CNRS-ENSI) and

Université de Caen Basse-Normandie

"Fundamental Interactions", ECT* Trento, June 21-26, 2004

3

context and plan

describe some searches for signatures of NP in weak decays, specifically sensitive to P and/or T violation

1. CP-even, P-odd correlation (muon decay)

2. CP-odd, P-odd correlation (neutron decay)


4

1. The longitudinal e+ polarizationin polarized muon decay

(initially motivated by the sensitivity of P -/P + measurements in nuclear

beta decay)


5

-decay phenomenology

ee GF

e

e

4-fermions point-like interaction:

• beyond SM: include all Lorentz invariants

decay amplitude parametrized by

g (W.Fetscher PLB

173(86)102)

= S,V,T interactions

, = L,R helicity of charged fermions

• in the SM (all others are zero)

1VLLg


6

parameterization of observables

PDG 02 V-A

r 0.7518 (26) 0.75d 0.7486 (38) 0.75h -0.007 (13) 0x 1.0045 (86) 1x' 0.998 (45) 1x'' 0.65 (36) 1h 0.012 (16) 0a/A -0.0002 (43) 0b/A -0.0015 (63) 0

39.035.01'''

xxx

Observables commonly expressed in terms of Michel parameters:

status

the parameter x’’ enters the angular/energy dependence of PL by the combination:

(present PDG value)


7

longitudinal e+ polarization

1

'''

)12(cos)23(

)12(cos1')cos,(

xxx

x

xxxPx

xPxPL

xx = Ee /E0 reduced positron energy

g

g

g

ge

g

g

g

g

g

g

g

g

VLL

TRL

VLL

SRL

VLL

TRL

VLL

SRR

VLL

VRR

VLL

VRL

*

*

2441

241'''

2

2

2

2

2

2

2

2

xxx

P

e+

PL sensitivity vs x and for P = 0.95

→ measure near = and x = 1

relation to exotic couplings


8

relative measurement

r -, r 0 : rates of positrons incident on the polarimeter for polarized and unpolarized muon decays (measured)

r

rr

A

Ak

0

1

avoids the precise determination of the polarimeter analyzing power

compare e+ polarizations between polarized and unpolarized muons:

sensitivity coefficient:

implementation• produce polarized muons

• maintain/destroy the muon polarization

• select backward emitted positrons near the end point

• measure the longitudinal polarization


9

realization

E3 area

muons are naturally produced 100%polarized from pion decay at rest

“surface muons”

(contamineted by “cloud muons”)


10

experimental setup

Al or Starget

Wien filter

PolarimeterSpectrometer

monitortelescopes

(B < 0.0004 T)

28.9 MeV/c + > 44 MeV/c e+

stop rate: 3x107 s-1 at 1.6 mA

e+/+ velocity separation

N(e+)/N(+) < 0.12


11

muon polarization

at 28.5 MeV/c: P = 0.94(1)

Hanle method

(with two plastic telescopes)

polarization vs muon momentum

“surface muons”

use two muon stop targets:

Al: P = 0.94 “polarized”

S: P = 0.10 “unpolarized”


12

energy and angular selection

pe = 50 MeV/c

pe = 29 MeV/c

12 < < 13

60% transmission

for Ee > 44 MeV

1.9T 2.7T 0.8T

selector tracker refocus

dump of beam positons


13

silicon tracker

1 2 3

d12 d23

e+

z

21

2

3

12d

23d

31d

determine momentum from helix geometry

redundancy constraint!

- 3 planes with 4 detectors each- 60x60 double SSD 1 mm pitch 300 m thick

resolution pe = 1.15(1) MeV/c


14

positron polarimeter

e

e

e

e

WC

WC

Vacoflux foils with oppositemagnetization

Hodoscope

BGO

scintillator

use two processes:

- Bhabha scattering

- Annihilation in flight

(have analyzing powers with opposite signs)

BHA: Aeff ~ 0.037

AIF: Aeff ~ -0.015

(incl. fraction of polarized electrons and foil orientation)

but similar FOM (luminosity)CoNiFe foils: 75x15x0.1 cm3 with 0.75mm active

region to reduce Brehmstralung events


15

hodoscope and calorimeter

• 127 BGO crystals, 55mm diam, 20cm long

• external magnetic shielding

• temperture stabilized T = ±2°

• resolution E/E = 10% at 42 MeV

• 7x7 plastic scintillators (x and y)

• 90x7 cm2 with single PM readout


16

measuring conditions

• two magnetized foils with opposite magnetizations (simultaneous)

• two directions of magnetization for each foil

• two orientations of the polarimeter: +45°, -45°

• two analyzing processes with opposite analyzing powers (BHA, AIF)

• two stop targets for polarized and unpolarized muons

• measure energy dependence of the longitudinal polarization

typical trigger rates:• total 15 kHz

• AIF 60/s

• BHA 250/s (consistent with MC simulations)


17

cluster recognition, event reconstruction,

cuts, ratios, asymmetries…

• triggers defined from scintillators and BGO

• SSD readout is slave

• event type sorted from hits in MWPCs, Hodoscope and BGO


18

preliminary results(X. Morelle, PhD)

Si energy (MeV)

5545

Asymmetries for all the runs -0.06

-0.04

-0.02

0

0.02

0.04

0.06Annihilation Bhabha

Al +45

Al -45

S +45

S -45Al +45

Al -45

S +45

S -45

5545 5545 5545 5545 5545 5545 5545

asymmetries of ratios under inversion of foils magnetization

PRELIMINARY! x” = 1.020 ± (0.062)stat ± (…)sys

(factor of 6 improvement if sys remains negligible)


19

status

• experiment did not acquired the planned statistics

• no present plans to make a new run


20

people and institutions

(thanks to R.Prieels)

J.Egger, N.Danneberg, J.Deusch, W.Fetscher, F.Foroughi, J.Govaerts, M.Hadri, Ch.Hilbes, K.Kirch, P.Knowles, K.Koehler, A.Kozela, J.Lang,

M.Markiewicz, R.Medve, X.Morelle, O.Naviliat-Cuncic, A.Ninane, R.Prieels, L.Simons, J.Sromicki and P.Van Hove

• Institut de Physique Nucléaire, UCL, Louvain-la-Neuve, Belgium

• Institut für Teilchenphysik, ETH, Zurich, Switzerland

• Paul Scherrer Institut, PSI, Villigen, Switzerland

• Département de Physique, Uni-Fribourg, Switzerland

• Laboratoire de Physique Corpusculaire, Caen, France


21

related projects

TRIUMF Weak Interaction Symmetry Test: “TWIST”

http://twist.triumf.ca/~e614/experiment.html

tracking of e+ from polarized muon decay

goal: detemine r, d, Px with a relative precision at the 10-4 level

prelim. results expected in 2004


22

2. Measurement of the R parameterin neutron decay


23

the R coefficient

ne

eneene

ˆ...ˆ

ˆ1)( JσpJσp

J NE

RE

AEWWee

eepn

decay rate function:

• the coefficients A, R, N, … probe the dynamics

• JTW parameterization: Ci , C’i (i = S, V, A, T )

e

pep

Pp

Jn


24

R and D in neutron decay

)(34.0 *AVCCImD

ATT CCCImT /)'(

AC

D : P-even T-odd R : P-odd T-odd

TSR 33.028.0ASS CCCImS /)'(

DFSI = 1.310-5 (10-6) RFSI = 910-4 (510-6)


25

measuring principle

eE

R eneˆ pJσ highest sensitivity to R for

mutually perpendicular vectors

e

pep

Pp

Jn

Mott scattering


26

experimental concept(J. Sromicki NIM A 440 (2000) 609)

• produce polarized cold neutron beam

• observe neutron decay in flight

• track low energy decay electrons

• use large angle Mott scattering

• trigger with “opposite” scintillator


27

Spallation neutron source SINQ

• target: “zircalloy” (Zr-Pb)

• D2O moderator

• liquid D2 vessel cold source

realization

FUNSPIN area


28

polarized cold neutron beam

• flux: 2×108 /(cm2·s·mA)

• ‹P› ≈ 97 %

• A. Schebetov et al.

NIM A 497 (2003) 479

• J. Zejma et al.

to be submitted to NIM A

FUNSPIN area


29

scheme of the experimental setup


30

photo galleryMWPC HODOSCOPE DECAY REGION


31

results from commissioning run

• Energy spectra of electrons from single track events

S/B > 3:1


32

Mott scattering analysis

cross section and Sherman function in Au

… Pb is better (higher Z) and cheaper!

- 1m evaporated Pb layer on 2m mylar

- 2 or 3 bands for 50x50cm2 active surface


33

a “golden event”


34

vertex reconstruction

positions of Pb scattering foils

(A. Kozela)


35

vertex signals

• after vertex reconstruction with VETO condition on

the hodoscope at the vertex side S/B > 10:1

• inclusion of hot spots of the setup geometry is in

progress to further improve S/B


36

comments

A

TT

A

SS

CCC

T

CCC

S

'

'

Im

Im

2. precision goal: R = 510-3

Em

AEm

N 116.0 SMSM

• “up-down” asymmetry probes R

• “left-right” asymmetry probes N

1. polarimetry control

the simultaneous measurement of N ≠ 0 provides a control of the polarimeter

Exclusion plot on S and T from beta decay experiments (±1)


37

interpretation

P. Herczeg 2004: constraints on |Im(aLS)| from R are hard to beat with Rn

Rn at 10-2 would require fine-tuned cancellations

→ make life less exciting…

… important considerations for new generation experiments


38

status and outlook

• The Mott polarimeter for the measurement of R in neutron

decay

is complete.

• The commissioning run in autumn 2003 was successful.

• The first data taking run starts next month.

• The measurement of R with an accuracy of 10-2 is expected

to be achieved within one year.

• The sensitivity goal of 510-3 seems feasible;

will be checked after first complete data analysis.


39

people, institutions, support

• Laboratoire de Physique Corpusculaire, Caen• Institute of Physics, Jegellonian University, Cracow• Institute of Nuclear Physics, Cracow• University of Alberta, Edmonton• St Petersburg Nuclear Physics Institute, Gatchina• University of Silesia, Katowice• Catholic University Leuven, Leuven• Paul Scherrer Institute, Villigen• Institute of Particle Physics, ETH Zurich

(thanks to K. Bodek and P. Gorel)

G.Ban, M.Beck, A.Bialek, K.Bodek, T.Brys, A.Czarnecki, W.Fetscher, P.Gorel, K.Kirch, St.Kistryn, A.Kozela, A.Lindroth, O.Naviliat-Cuncic,

J.Pulut, A.Serebrov, N.Severijns, E.Stephan and J.Zejma

support for PhD students

Documents

P and T violating correlation in muon and beta decays