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ATHENA: a High Performance detector for Low Energy physics. Univ. of Tokyo Ryo FUNAKOSHI ATHENA collaboration. Out Line. Introduction - antiproton facility at CERN ATHENA experiment (focused on detector) - setup (trap + detector), electronics, feature Detection of antihydrogen

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athena a high performance detector for low energy physics

ATHENA: a High Performance detector for Low Energy physics

Univ. of Tokyo

Ryo FUNAKOSHI

ATHENA collaboration

out line
Out Line
  • Introduction

- antiproton facility at CERN

  • ATHENA experiment(focused on detector)

- setup (trap + detector), electronics, feature

  • Detection of antihydrogen

- detection scheme

  • Future experiment

- antihydrogen trap (just idea)

introduction antiproton decelerator ad
Introduction:Antiproton Decelerator (AD)
  • Low energy antiproton source (only one)
  • Stochastic & electron cooling
  • Antiproton: 3.5 GeV/c -> 100 MeV/c
  • Pulse beam, every 85 s (~2 x 107 antiprotons)
introduction antiproton facility at cern
Introduction:Antiproton facility at CERN

ATRAP

ATHENA

ASACUSA

AD

1999-

LEAR

1986-1996

Three experiments in AD hall:

Athena --- Antihydrogen

Asacusa --- Pbar He, etc.

Atrap --- Antihydrogen

  • 1992 Proposed by Munger et al.:
  • pbar + Z → hbar
  • 1996 9 events antihydrogen
  • (however life time ~40 ns)
introduction athena collaboration
Introduction:ATHENA collaboration

Univ. of Aarhus, Denmark Univ. of Brescia, Italy Univ. of Genova, Italy CERN, Geneva, Suisse

Univ. of Pavia, Italy Univ. of Rio, Brazil Univ. of Swansee, Wales (UK) Univ. of Tokyo, Japan

Univ. of Zurich, Suisse INFN, Italy LANL, USA

athena instruments
ATHENA Instruments

ATHENA apparatus

Features

  • strong e+ source
  • high performance detector
  • plasma manipulation
athena experiment overview of apparatus
ATHENA experiment:Overview of apparatus

Antiproton catching trap

Positron accumulator

Mixing trap

Antihydrogen detector

athena experiment main detector
ATHENA experiment:Main detector

・ compact, operation under strong B field

・ large solid angle > 80%

・ high granularity;

Si : 2 layers, ~8000ch. -> charged particles

CsI : 192ch. -> 511keV photons

athena experiment silicon module
ATHENA experiment:Silicon module

Thickness: 380mm

  • Double sided sensors
  • Read out VA2_TA chip (manufacture)
athena experiment csi crystals
ATHENA experiment:CsI crystals

Resolution FWHM ~ 18%

Efficiency ~ 20 %

VA2_TA chip

athena experiment installation
ATHENA experiment:Installation

<Trap>

P<10-12mbar, T~15K

Cold nose

<Detector>

P~10-9mbar, T~130K

athena experiment antiproton catching
ATHENA experiment:Antiproton catching

Segmented Si (67 µ) beam counter

Antiproton Capture Trap

~10000 antiprotons per AD shot

athena experiment imaging by silicon detector
ATHENA experiment :Imaging by Silicon detector

non-destructive monitoring system

YZ-projection

Event display

3D image of antiproton annihilations

XY-projection

athena experiment imaging by silicon detector1
ATHENA experiment :Imaging by Silicon detector

M. C. Fujiwara et al., Phys. Rev. Lett. 92, 065005 (2004)

non-destructive 3D image of antiproton annihilations

cold antihydrogen production scheme
Cold antihydrogen:Production scheme

qgg

104 pbars

108 e+

qgg

  • mixing 104 antiprotons + 108 e+
  • annihilation of produced antihydrogen

-> escape from B confinement

-> charged particles from p annihilations

-> two 511keV photons from e+ annihilations

(back-to-back)

  • Vertex reconstruction by trace of charged particle paths
  • (Si-strip)

Si-strip

annihilation

  • Extrapolation of two 511keVphotons to the vertex (CsI crystals)

Antihydrogen production

2.5 cm

3T

Antihydrogen event

Opening angle between two photons;

cosqgg = -1

CsI crystals

cold antihydrogen detection efficiency
Cold antihydrogen:Detection efficiency

Detection scheme

Antihydrogen annihilation

~50%

Vertex reconstruction

~10%

Opening angle selection

( 2 x 511keV photons)

~5%

Antihydrogen events

Total efficiency ~ 0.25%

50,000 antihydrogen

cold antihydrogen cold antihydrogen i
Cold antihydrogen:Cold antihydrogen I

Antiproton annihilation distribution

`Cold mixing’

`Hot mixing’

cold antihydrogen cold antihydrogen ii
Cold antihydrogen:Cold antihydrogen II

131± 22 GoldenEvents

  • Antiprotons only
  • Displaced 511keV energy window

1. `Hot mixing’

 suppress antihydrogen production

for the future estimated temperature
For the future :Estimated temperature

Isolated hbar spatial distribution

(“Cold mix.” – “Hot mix.”)

Model

  • Hbar formation before thermal equilibrium
  • Including the plasma rotating (80kHz)
  • Two-temperature Gaussian distribution

No Te+ dependence

Best fit with Taxial = 10 x Tradial

N. Madsenet al., Phys. Rev. Lett. 94, 033403 (2005)

Temperature of antihydrogen > 150K

(ATHENA experiment)

for the future motivation
For the future:Motivation

High precision tests for CPT

(e/m)

(matter)(antimatter)

same mass & life time, same & opposite charge

2005

Impossible to do with ATHENA type equipment;

Once antihydrogen has been trapped, any type of precision measurement can be contemplated

for the future antihydrogen trap i
For the future :Antihydrogen trap I

Idea -neutral atom trap -

Well depth ~ 0.7 K/T

Aside: high n-states could have higher m

for the future antihydrogen trap ii
For the future :Antihydrogen trap II

+

ATHENA type (trap + detector)

amulipole trap

+