# Presentation: 947496

## A Test of Time Reversal Invariance in Stopped Kaon Decay   K+→0+ 

- Michael D. Hasinoff
***University of British Columbia***
***for the KEK --  E246 collaboration***
**Oct 24, 2005   PANIC’05**
**Santa Fe, NM**

-  Introduction and Theory
-  Experimental details
-  Analysis method
-  Final results for the entire data set
-  J-PARC proposal

## E246 collaboration

- Japan	       ● KEK  ● Univ. of Tsukuba,
-  	       ● Tokyo Institute of Technology
- 	       ● Univ. of Tokyo   ● Osaka Univ.
- Russia        ● Institute for Nuclear Research -- Moscow
- Canada       ● TRIUMF   ● Univ. of British Columbia
- 	       ● Univ. of Saskatchewan   ● Univ. of Montreal
- Korea	       ● Yonsei Univ.   ● Korea Univ.
- U.S.A.	       ● Virginia Polytech Institute  ● Princeton Univ.
- Taiwan	       ● National Taiwan Univ.

## Transverse Muon Polarization in K+→0+ 

*K*3 decay form factors and  T violation

**Triple product correlation**
**--changes sign under T****op**

**p******

**p******

## Model predictions for PT

-       Model                                ***K*****+**** ******** ********0********+******** ****       *****K*****+**** ******** ********+******
**Standard Model**  		          **< 10****-7****                       < 10****-7**
**Final State Interactions ****	****          < 10****-5**** ****                                ****< 10****-3**
**Multi-Higgs  **** ****	****	****        ****	****          ******** ****10****-3****                       ******** ****10****-3 **
**                                          *****P******T *****(*****K*****+**** ******** ********0********+********)  ********  3 *****P******T *****(*****K*****+**** ******** ********+********) **
**SUSY with squarks mixing ****  ****	****          ******** ****10****-3                                 ******** 10****-3**
**                                                         *****P******T *****(*****K*****+**** ******** ********0********+********)  ******** - 3***** P******T *****(*****K*****+**** ******** ********+********)**
**SUSY with***** R*****-parity breaking             ******** 4 x10****-4                         ******** 3 x10****-4**
**Leptoquark model****     ****	****	****          ******** 10****-2                                ******** 5 x10****-3**
**Left-Right symmetric model****	****	****0****	****            < 7x10****-3**

*** ******P******T  *****(*****K*****→***** *************** ****and**** *****P******T  *****(*****K*****→***** *************** ****are**** ****complementary.**

## KEK E246 experiment

- _Stopped __*K*_+ experiment with a SC _toroidal spectrometer_
- Measurement of _all decay kinematic directions_
- Double ratio measurement with small systematic errors

- Features

- History

**1992-1995** :   detector construction
**1999**** **         :   first result (~1/3 of data) [ Phys.Rev.Lett. _**83**_ (1999) 4253 ]
-                                  **P****T  ****= -0.0040** **± 0.0040(stat) ± 0.0010(syst)     **
-                               **Im**********= -0.0230 ± 0.0070(stat) ± 0.0030(syst)**
**2004****   **       :   final result ( 11.8 x 106 events ) [ Phys.Rev.Lett. _**93**_ (2004) 131601 ]
-                                  **P****T  ****= -0.0017** **± 0.0023(stat) ± 0.0011(syst)    ****< 0.005 (90% CL)**
-                               **Im**********= -0.0053 ± 0.0071(stat) ± 0.0036(syst)    ****< 0.016 (90% CL)**

- Other Physics Result

*  **K*+→********P****T  ****= -0.0064 ± 0.0185(stat) ± 0.0010(syst)**
-                                      [V.Anisimovsky et al., Phys.Lett. B562 (2003) 166]

## Superconducting toroidal magnet

## E246 experimental setup

- End view

- Side view

- [J.Macdonald *et al*.; NIM A506 (2003) 60]

* **K*+→**0**+**

## Determination of PT

**	****CW counter of one sector =**
**     ****CCW counter of the adjacent sector**
-      **Efficiencies of the positron counters **
**     ****are cancelled out.**
- _ __**Double ratio measurement**_
**  ****P****T****(π****0**** forward) & P****T****(π****0**** backward)**
-   **P****N**** contribution to systematic error is **
**           ****drastically reduced. **

- Determination of PT

**Stopped K****+ ****beam**

- =

## Muon polarimeter

- Cross section

- One-sector view

## Experimental data

***K*****+********3****  event selection**

***e*****+**** ****time spectra**

- CsI(T*l*) analysis : 

- TOF analysis

- Momentum
- analysis

*e*+ time spectrum

## Final Result

***P******T***** = - 0.0017 ± 0.0023(stat) ± 0.0011(syst)**
**  ****( |*****P******T *****| < 0.0050 : 90% C.L. )**
**Im**********= - 0.0053 ± 0.0071(stat) ± 0.0036(syst)**
**  ****( |Im**********| < 0.016 : 90% C.L. )**

- Limited by Statistics

- Backgrounds—
- --accidentals   5-10%
- --K+0         5-10%

## Systematic errors

**Source of Error****	********12****	*****fwd/bwd*****	****         ***********P******T***** ****x 10****4**
*e*+ counter r-rotation	o	o	0.5
*e*+ counter z-rotation	o	o	0.2
*e*+ counter **-offset	x	o	2.8
*e*+ counter r-offset	o	o	<0.1
*e*+ counter z-offset	o	o	<0.1
**+ counter y-offset	x	o	<0.1
- MWPC**-offset (C4)	x	o	2.0
- CsI misalignment	o	o	1.6
*B* offset (**)	x	o	3.0
***B*** rotation (***x*)	x	o	0.4
***B***** rotation (*****z*)	**x**	**x**	**5.3**
*K*+ stopping distribution	o	o	<3.0
********+ ****multiple scattering**	**x**	**x **	**7.1**
- Decay plane rotation (***r*)	x	o	1.2
- Decay plane rotation (***z*)	x	**x**	0.7
*K*2 DIF background	x	o	0.6
*K*+ DIF background	o	x	< 1.9
**Analysis**	-	-	**3.8**
**Total Systematic Error**			**11.4**

- **Sum 12 gaps : 12-fold rotational**** ****cancellation**
* ****fwd/bwd*****        :  ********0**** forward/backward cancellation**

## Model implications

***L***** **= (2√(2)*G**F*)1/2 [***i**U**L**KM****D****D**R* + ***i**U**R**M**U**KD**L* +* ****i**N**L**M****E****E**R*] *H**i**+*  + *h.c.*

- Im** = Im(**1**1***) ×(*v*2 /*v*3)2 × (*m**K* / *m**H*+)2
-        = Im(**1**1***) × (*m*K / *m*H+)2

*v**i*  : vacuum expectation values
- i, i, i : mixing matrix elements

- Three Higgs doublet model

-  **|Im**********| < 0.016 (90% C.L.) ******** Im(**********1**********1***********) < 544    (at *****m******H ******= m******Z *****)**
-             **cf*****.*****   BR (*****B→X***********************)     ******** Im(**********1**********1***********) < 1900  (at *****m******H ******= m******Z *****)**

- Neutron EDM in 3HD model

*d**n* ≈ 4/3 *d**d* ≈ Im(**1**1***) × *m**d** */ *m**H*2

*v*2/*v*3 ≈ *m**t **/ m*** ≈ 100   [R.Garisto and G.Kane, Phys. Rev. D44 (1991)2789 ]

-  |**Im**********| < 0.016 (90% *****C.L.*****) ******** *****d******n*****       ****<  7  ****× ****10****-27 *****e***** cm**
**                               ****cf.        *****d******n*****exp****  < 3.1****×****10****-26**** *****e***** cm    **(2005)

**−**

## Necessary Improvements for J-PARC T-Violation Experiment 

- Higher K+ Beam Intensity
- Improved K/ ratio
- Improved  vertex determination
- Better determination of the muon stopping position  active polarimeter

## J-PARC T violation experiment 

-  Methodology :
-  Stopped *K*+ method rather than an in-flight decay experiment
-  Double ratio measurement in the decay kinematic space
-  Longitudinal field on the *P**T* component
-  Desirable detector :
-  Larger *K*3 acceptance than E246
-  Simultaneous *P**T* measurement of *K***3 and *K*
-  Smaller instrumental systematic errors (in ***B****z* and ***z*)
-  Sensitivity goal :

-  J-PARC experiment :
-              *******P******T******syst*****(JPARC) ~ 1/10 *********P******T******syst*****(E246) ~ 10****-4**
- *******P******T******stat*****(JPARC) ~  *********P******T******syst*****(JPARC) ~ 10****-4**

## Strategy

-  **Upgraded E246 detector in Phase 1**
-  E246 was statistics limited
-  well known detector systematics
-  beam intensity in Phase 1 is limited
-  several improvements in detector elements
-  Active muon stopper
-  Magnet to control muon spin
-  **Phase 2 experiment with the highest sensitivity**
-  completely new detector
-  0 detection based on a new concept
-  utilize the highest beam intensity of  ~107/s
-  optimization of detector acceptance  --
-    for both *K*3 and *K***

## Phase1: Upgraded E246 setup

-  ***eff* ~ 1/4 ***Al*

**Good resolution for radial direction but not for axial direction:--**
** ******** *****Two orientations are necessary***

- Active polarimeter and Magnet to control muon spin

-  Measurement of
-  **+ decay vertex
-  *e*+ energy and angle

-  Analysis

***Highest analyzing power***

## An Option with Magnetic Field

## Expected K3 sensitivity

|  | New detector | E246 upgrade |  E246(KEK) |
| --- | --- | --- | --- |
| K+ beam intensity
K+ stopping efficiency
Net runtime	
Acceptance
Number of decays
fwd/bwd events
Analyzing power
PT kinematic atten
 | 107/s (Phase 2)
0.30
107 s
2.0×10-4
2.0×1010
1.3×1010
0.3
0.8 | 106 /s
0.40
107 s
3.8×10-4
1.5×109
 5.0×108 
 0.27
1.0   | 105 /s
 0.40 
   1.5×107 s
 5.5×10-5
3.3×107
1.1×107
0.27
~0.70 |
| PT      K3
PT      K | 4×10-5 
7×10-5 | 1.13×10-4
- |  2.3×10-3
 - |

- Detailed Proposal will be submitted – March 2006.

- Expected *K*3 sensitivity

## Summary & Outlook

-  Transverse muon polarization in *K*+→**0**+** decay is a good probe of
-     CP violation beyond the standard model.
-  The final result of our KEK-E246 experiment shows no evidence for
-     T violation with  **Im**********= - 0.0053 ± 0.0071(stat) ± 0.0036(syst)** ,  or
-     |**Im**********| <0.016 (90% C.L.)**. This is a factor of 3 better than the previous
-     BNL *K**+* experiment but it is statistically limited.
-  This limit constrains the parameters of some non-standard CP violation
-     models with high sensitivity.
-  Our proposed next generation  ***P******T***** ** experiment at J-PARC will allow us to
-    reduce this limit by more than a factor of 10.

**New Collaborators are Very Welcome !!**

## Other T violation studies

-                   _
*K*0 - *K*0 system
- CPLEAR      first direct observation of
-                **_**           **_**
-    *K*0 → *K*0  vs.  *K*0 → *K*0 asymmetry   **( 0.66 ± 0.13 )%**  ; 1998
- KTeV           observation of CP-odd & T-odd asymmetry in
-    *K**0**L* → *e*+*e*-                 **( 13.6 ± 2.3 (stat) ± 1.2 (syst) )%** ; 1999
- Other systems :   up to now only upper limits
- Neutron EDM (P and T violation)         ** ****|*****d******n*****| < 0.31 x 10****-25**** *****e***** cm** ; 2005
- Nuclear beta decay (*R *- parameters)     ***R***** = ( 0.9 ± 2.2 ) x 10****-3** ;   2003
- Muon decay (*e*+ polarization *P*T2 )    **<*****P******T2 *****> =( -3.7 ± 7.7 ± 3.4 ) x10****-3** ; 2005
*                                                                                         *
-  *B* meson system : theoretical suggestions
*P**T* (*B* → *D*),  *B *→ *VV*,  *B *→ *K***l*+*l*-,  *etc*.

-  Extra slides

## Triple Product Correlation

**S********Trans**

**S********Trans**

**Triple Product Correlation**

##   Double ratio measurement

**Counter(i) is CW cter**
**for gap (i) but CCW **
**cter for gap (i-1).**

## J-PARC Facility  KEK and JAERI

- J-PARC Facility  **KEK and JAERI**

**J-PARC = Japan Proton Accelerator Research Complex**

## Phase 1 and Phase 2 of J-PARC

* **K-*decay experiments will be performed in the Hadron Experimental
-      Facility using the slow-extracted beam

-  slow extraction

## Beam parameters 

- Phase 1
- Day-1	          Linac    180 MeV        30 mA       25Hz	                     RCS         3 GeV       0.6 MW
- 		                     MR         40 GeV      400 kW
- Next Stage      Linac   400 MeV        50 mA       25Hz                        RCS        3 GeV       1.0 MW
**	****	****                      **MR        40 GeV      670 kW
- Phase 2
-                                     Linac   600 MeV       50 mA        50Hz
- 		                      RCS       3 GeV       1.0 MW
-                             MR        50 GeV     750 kW
-    (*MR parameters are for the fast extraction beam operation)*