# Presentation: 024292

## Pionic Hydrogen – Precision Measurements at PSI 

- J. Marton
- Stefan Meyer Institut (SMI) / ÖAW
- on behalf of the Pionic Hydrogen Collaboration @ PSI

- aIoannina –  bCoimbra –  cSMI –
-  dJülich –  eParis –  fPSI

## Physics Goals

- N coupling constant (using Goldberger Miyazawa Oehme sum rule)
- pion-nucleon sigma term (measure of chiral symmetry breaking)

- High precision values for the hadronic shift
- and width of the 1s ground state of pionic hydrogen
** ****pion-nucleon scattering  lengths **(isoscalar, isovector)
-     with an accuracy at the percent level

- scattering lengths  basis for comparison of changes
- 			 in the nuclear medium

## Pion-Nucleon Scattering Lengths

- shift data from pionic hydrogen and deuterium, width from pionic hydrogen (Schröder et al.,2001)

- For e.m. contributions see talk by
- T.E.O- Ericson at this conference (IV.7.)

## Electromagnetic Cascade of p

- Pion decay
- ~10-8 s slow compared to reaction rates

- precise QED calculations
- advanced cascade theory

- p is not an isolated system  interaction with hydrogen

## Principle  of  Set-Up  

**	****high **_**stop density**_
**	****	****	****	****	****	**
**	********   ****high    X - ray line yields**
**	********   ****bright X - ray source**

- 	_position & energy resolution_
-  background reduction by analysis of
-      CCD  hit pattern

- spherically bent Bragg crystal

**  ****ultimate energy resolution**

## SET-UP at  PSI

**      ****crystal spectrometer**
***    ******spherically bent  crystals***

**CCD X-ray detector**
***      ******2 ************ 3  matrix ***

**X-ray tube**

** **

- cryogenic target

**     ****cyclotron trap II**

## Experimental Method

- Bragg
- crystal

- CCD X-ray
- detector

- Target and cyclotron trap

## Cyclotron Trap with Target and Degraders

***     *********
- X - rays

-   beam
- 

******

******

- stop efficiency
- fstop   density
-          1% @ stp

- 109 /s

- super-conducting split coil magnet

## Spherically curved Bragg crystal

***100 mm***
******

## Large - Area  Focal  Plane  CCD Detector

***N. Nelms et al., Nucl. Instr. Meth 484 (2002) 419***

- 2  3     CCD 22  array

- pixel size  40 m  40 m
- 600  600  pixels per chip
- operated at  – 100°C
-   150 eV   @ 4 keV
- X    90%

**image area**

***storage area***

***flexible boards***

***cooling (LN******2******)***

****

******

## Features of the Experiment 

- 	p=112 MeV/c, ~ 109 -/s
- cyclotron trap for small stop volume
-     and high stopping efficiency
- Light weight cryogenic target
- 	for wide density range
- spherically bent Bragg crystals
- 	characterization by ECRIT X-ray source
- position sensitive X-ray detection with CCD array:
- 	CCD-22 background reduction by shielding
- 	and pixel analysis of CCD data
- calibration lines (pionic oxygen)
- 	measured in parallel

- Features of the Experiment

## πp Hadronic Shift and Width 

- πp Hadronic Shift and Width

- e.m. transition
- without strong
- interaction

- attractive shift

- Goals: Shift 0.2%
-            Width 1%

- Molecular effects

- Doppler broadening
- Coulomb deexcitation

- required resolution:
- 1:100000

- careful study of
- small effects

- Stability & Calibration

## extention of parameter space: 
	measurements of shift and width with different

Doppler broadening of width to be measured with 
	muonic hydrogen X-rays (no hadronic interaction)

- extention of parameter space:
- 	measurements of shift and width with different
- Doppler broadening of width to be measured with
- 	muonic hydrogen X-rays (no hadronic interaction)

- Experimental Procedure

-  densities

-  X-ray transitions (4p-1s, 3p-1s, 2p-1s)

- Investigations on
-     molecular effects

- Coulomb transitions
- effecting the width

##  H(3p-1s) energy	   no density dependence identified

** **
**	****	****	****	****	**

******1s**** = + 7.116 ******** 0.008 ******** 0.007 eV**** **

*********E******QED ******= ± 0.006 eV ***
***P. Indelicato, priv. comm******.***

****

******* ******previous experiment***

***LH******2***

***previous experiment ***
***ETHZ-PSI******	******H.-Ch.Schröder et al.***
***	******Eur.Phys.J.C 1(2001)473***

- Density Effect ?

**Molecular formation ("Vesman“ mechanism) **
- p + H2  [(pp) p] ee
***	***

## Electron Cyclotron Resonance Ion Trap 	cyclotron trap (4) + hexapole magnet (2) (D. Hitz  et al., Rev. Sci. Instr., 71 (2000) 1116)

****

***large mirror ratio***
***B******max****** / B******min  ******!***

***argon****** / oxygen  (1/9)***
***1.4************10******-6****** mbar***
***HF  6.4 Ghz***

***	******	***Response Function

- H- and He-like electronic atoms
- Tion   5 eV     "cold" plasma
- _ __narrow_ X-ray transitions
-     X  =  10 - 40 meV
-  high X-ray intensity: short measuring time

- First plasma inside ECRIT

##  ECRIT  and  Crystal SpectrometerD.F.Anagnostopoulos et al., Nucl. Instr. Meth. B 205 (2003) 9

***CCD detector***

***aperture***
****

***6.4 GHz, 450 W***

-  response function very well understood

## Line Width Analysis

- previous experiment
- H.-Ch.Schröder et al.
- Eur.Phys.J.C 21 (2001) 473

- _not_
- corrected for
- Coulomb de-excitation
- crystal resolution
-  subtracted

***    ******15                       3.5                       3.5        28.5        LH******2******                  10       bar***

## Hadronic Width (preliminary)

- Hadronic width – corrected for Doppler effect
- due to Coulomb de-excitation

- Preliminary average value for the hadronic width
- 1s = 785 ± 27 meV

## Muonic Hydrogen

*Coulomb de-excitation*
*   **low-energy component*

- Coulomb de-excitation
-    *high-energy components*

- -----    Crystal response ECRIT 2004
- μH      R-98.01  December 2004

##  Results on Pionic Hydrogen

** ****	****	****                                    ****	****      ****	****	****	**
** ****	****   ****	****	****	****   ****	****    ****	****   ****	****	****	****   **PSI Experiment R98-01
**	****	****	****	****   **previous
-  					exp.	**	****	****   **1. step**	****	****         goal**
** **
******1s ****/********1s****	****	****	**0.5%	****** ****	**** ****	****  ******** 0.2%****	****	****  ****	****   ****0.2% reached**
** **
** ********1s ****/********1s**			  7 % 			  **** **3** **%**		**	****         ****1%**** **

-  Results on Pionic Hydrogen

- Work in progress:
- H  	Coulomb de-excitation  analysis
- H	high statistic measurement (presently running)

## Status of πp Experiment

- Density dependence studies of the 1s

-  no effect of molecular effects at our accuracy found

-  value consistent with result of previous experiment

-    Measurement of transitions from 4p, 3p and 2p to 1s

-  influence of cascade processes on width
-    (due to Coulomb de-excitation) visible  Doppler effect

-    ECRIT  response function extracted

-    Precision measurement of μp X-ray spectrum

-  study of the Doppler broadening due to Coulomb transitions

## Outlook 

- Thank you for your attention

- High statistic data  most precise width determination