Study of b-n correlations with LPCTrap

Dominique Durand

LPC Caen, ENSICAEN, Université de Caen, CNRS/IN2P3, Caen, France

On behalf of the LPCTrap collaboration

Laboratoire de Physique Corpusculaire - Caen

Outline

Motivation

Physics case and measurement principle

Experiments and results

Summary

EXON 2012

STANDARD MODEL of Particle Physics is a very powerful and predictive model (recent Higgs probable discovery) but it is probably not complete

Questions: n mass hierarchy, strong CP problem, matter/anti-matter, dark energy/matter

Test at low energy:

high precision measurements search for very small deviations from SM predictions

EDM’s, correlations (A, a, b, B, D, R, ….), g-2…

search for very rare (presumably forbidden) processes neutrinoless double b decay, proton decay,

…

High precision and high energy experiments are complementary

• observables linked to are sensitive to abn

• Recoil Ion (RI) momentum spectrum

Measurement of the beta neutrino angular correlation parameter abn

E: energy and velocity of the beta particleWo(E): phase space distribution as given by the Fermi theory of beta decay: angle between the antineutrino and beta particle

2+

+b-

b decay rate:

cos)(),(c

vEWEW βνa10

b decay and the weak interaction

SM Test pure vector axial interaction theory study through b decayabn is a function of the coupling constants

• Gamow-Teller Axial / Tensor

• Fermi Vector / Scalar CL : 95.5%

Exotic currents (beyond SM) tensor/scalar

07.0C

C

09.0C

C

V

S

A

T

Goal: new physics orImprove constraints on couplings

b decay, Vector -Axial, abn

- angular correlation coefficient measurement a

with relative statistical uncertainty less than 0.5%deviation from abn=-1/3 or 1 (SM) might reveal existence of new particles: leptoquark bosons …

abn (CV, CS, CA, CT, MF, MGT) : -b n angular correlation parameter

Pure F : aF (CV, CS) = +1 (SM, CS = 0)

Pure GT : aGT (CA, CT) = -1/3 (SM, CT = 0)

Mirror transitions :

• Analysis of available data (5 nuclei)

competitive with neutron/pion decay

• Valuable alternative to 0+->0+ transitions

• Several parameters to be measured: T1/2, BR, Q, r

and to be computed (corrections)

Transition |Vud|Super-allowed pure FermiSuper-allowed mirrorNeutronPion

0.97425 (22)0.9719(17)0.9746 (19)0.9728 (30)

& abn (r) = (1- r ²/3)/(1+ r ²)

For mirror transitions : r =GT/F

O. Naviliat Cuncic et al., PRL102 (2009)

CKM matrix and abn

Proceedings of CKM2010, the 6th International Workshop on the CKM Unitarity Triangle. T Sparado , A. Young

• observables linked to are sensitive to abn

• Recoil Ion (RI) momentum spectrum

• Ion trapping techniques are universal (several nuclei)

- LPCTrap: a bn deduced from RI ToF measurement

- ions almost at rest and well localized

- open configuration, few dead zones

• Precision measurement Da bn / abn <1%:

very difficult experiment:

systematic effects such as the

RF field ToF spectrum deformation

«shake-off» ionization probability required

How to measure abn

Transparent Paul Trap

V-A 6He+ pure GT transition, tensor couplingabn=-1/3High Q value, RI (6Li) up to 1.4 keVT1/2 high rate and efficient transmission to the trap

Vud and V-A

35Ar+, Mirror 35Cln+ scalar coupling, mixed transition correctionsa bn =0.904High Q value but heavier ion RI (35Cl) up to 450 eVT1/2 high rate and efficient transmission to the trap

Other candidates: 19Ne, 37K, 39Ca

Nuclei of interest

SPIRAL 6He beam

10 keV

DE ~ 20eV

Paul trap

Effective potential

1-2 V

Beam-handling

Beam characteristics :

- 10-30 keV, 80 p mm mrad

- rate : ~ 108 ions/s

LIRAT

LIRAT

Production target ECR source

LPCTrap

LPCtrap@GANIL/SPIRAL1

Beam line preparation

• Ions bunches

• Cycle period: 200ms(accumulation)

Beam 6He+

~2 108 6He+/s ~5 104 6He+/s trapped ions

Total efficiency: ~2.5 10-4

RFQCB:

• High-voltage platform

Buffer-gas cooling technique: H2 or He

Ion bunches

• Continuous voltage: longitudinal confinement

• RF field: radial confinement

• Cycle period: 200ms (accumulation)

1meter

Detectors and trap

• Detection in coincidence of recoil ion (RI) and b particle• ToF measurement ( b detection: START, RI detection: STOP)

Post-acceleration between the two collimators (Installed 2009)

50 cm free flight tube charge state separation (identified by ToF)

Time of flight:Free flight tube

MCP

• Beta position• Eβ

Recoils b-

telescope

6He+ bunch

Charge state separation:Free flight tube

MCP with delay line anode

MCPPSD

Ion trap

Silicon + plastic scintillator + PMTPost-acceleration

Recoil ion detector design

Grounded collimator

Grid MCPPSDAcceleration electrode

Collimator

Focusing electrode

LPCTrap : simultaneous measurement of abn and the «shake-off»probability

• Focusing electrode to collect recoil ions with maximal efficiency

• Geometry design and bias voltages estimation with “SIMION” software

• Successfully tested during four days in November 2010

6He+ :experimental results (2006-2010)

Pshake-off = 0.02339(35)stat(07)syst

PRL (Couratin et al.) 108 (2012) 243201

-0.36 -0.35 -0.34 -0.33 -0.32 -0.31 -0.30 -0.29

LPC-trap (coincidence)

Vise (coincidence)

aGT

in 6He

SM

Johnson (inclusive) 1963

1963

2010

Vise (coincidence)

Result: abn= - 0.3335(73)stat(75)syst

SM value = -1/3 PRL (Fléchard et al.) 38 (2011) 055101

( Dabn/a bn ) stat ~2%

Improve statistics also improve systematic uncertainties- effect of ion cloud temperature- effect of b back-scattering

6He+ Pure GTLimit on Tensor105 events

6He+ : experimental results (2006-2010), shake off

• Complete Monte-Carlo simulation w/ all systematic effects: RF fields, ion cloud characteristics, detectors response functions...

• Experimental spectrum fit w/ Pshake-off as free parameter assuming abn = -1/3

Experiment: ~4 days, Intensity ~108 pps, ~1.2 106 «true» coincidences

• High precision: DPshake-off =3.6 10-4

• Excellent agreement: theoretical value

of 0.0233

Pshake-off = 0.02339(35)stat(07)syst

PRL (Couratin et al.) 108 (2012) 243201“exceptional research” from APS

Data analysis still in progress GOAL: a bn estimationPreliminary: agreement w/ SM valueRelative stat. uncertainty < 0.5%

2000 2500 3000

-4-2024

10

100

1000

10000

Nor

mal

ized

resi

dual

sC

ount

s

TOF (ns)

experiment fit

Li3+

Li2+

35Ar+ : experiments results (2011-2012)

2000 4000 6000 8000 100000

5000

10000

15000

20000

25000

30000

Cl4+

Cl3+

Cl2+

Cou

nts

Time of flight (ns)

Cl+~1,5 106 "good events"

2011 commissioning run 2 days2012 8 days run @GANIL/LIRAT

expected final uncertainty Dabn (stat) < 0.002

full analysis is underway

35Cl charge state distribution

3 - 4 107 35Ar+/s incoming beam with ~2.5 x 108 contaminants/s

2 - 3 x 104 trapped 35Ar+ ions (every 200 ms)

Implantationtape station

Multi Reflection Time Of Flight Mass Spectrometer(MR-TOF-MS needed for new beams)

taccu ~ 1-10ms taccu ~ 100ms

Main RFQSmall RFQ

("rebuncher")

New chamber

PREMS: re-submitted to the ANR

Cryotrap

Vanne DN200CFTurbo V1000

Translation Espion

JaugeGaz

Translation miroir 45�

Translation Source6 DN200CF

Miroir

Enceinte Ø700 int

At least a factor ~ 10 in statistics

Precision measurement of the b-decay of exotic nuclei can probe

the weak interaction part of the Standard Model: abn V-A, Vud

LPCTrap is a universal tool that measures accurately abn for

several nuclei of interest and provide shake-off probabilities

Near future: Ne19 experiment accepted by GANIL PAC

Future: new beams and new apparatus

- PREMS: renewal of the experimental set-up on the LIRAT beam line

- new exotic beams and facilities are needed S3/DESIR@SPIRAL2

Summary & future plans

LPC CAEN :

Claire Couratin (PhD-2013)

Dominique Durand

Xavier Fabian (PhD-2015)

Xavier Fléchard

Etienne Liénard

François Mauger

Oscar Naviliat-Cuncic

Gilles Quéméner

Philippe Velten (PhD-2011)

GANIL: Pierre Delahaye

Bertrand Jacquot

Jean-Charles Thomas

CIMAP: Alain Méry

and the LPC technical staff

also thanks to the GANIL beam operators

KUL Leuven:

Martin Breitenfeldt

Simon Van Gorp

Tomika Porobic

Nathal Severijns

EXON 2012

WITCH ISOLDE CERN

Measure abn with a precision betterthan 0,5 %

ISOLDE+ REXTRAP (beam handling)

Penning trapsRetardation spectrometerMain isotope 35 Ar +Scalar searches

EXON 2012

WITCH ISOLDE CERN

After solving all kind of problems

Local penning, mechanical…

Data Obtained in 2011 with 35Ar

abn = 1.12 (33)stat

SM value of a =0.9004(16).Still a lot to measure and simulate

Next run Oct 2012

EXON 2012

We are not alone…

From N. Severjins, KUL