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Epiphany Conference January 6 - 8, 2005, Crakow, Poland. COSY-TOF research on Ө +. Wolfgang Eyrich Physikalisches Institut, University of Erlangen, Germany for the COSY-TOF collaboration. supported by German BMBF and Forschungszentrum Jülich.

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Epiphany Conference, Cracow, 2005, Wolfgang Eyrich, University of Erlangen

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Epiphany conference cracow 2005 wolfgang eyrich university of erlangen

Epiphany Conference

January 6 - 8, 2005, Crakow, Poland

COSY-TOF research on Ө+

Wolfgang Eyrich

Physikalisches Institut, University of Erlangen, Germany

for the COSY-TOF collaboration

supported by German BMBF and Forschungszentrum Jülich

Epiphany Conference, Cracow, 2005, Wolfgang Eyrich, University of Erlangen


Epiphany conference cracow 2005 wolfgang eyrich university of erlangen

Content

• Introduction

• The COSY-TOF experiment

• Evidence on Θ+ from pp  Σ+K0p

• Ongoing and new activities

• Outlook

Epiphany Conference, Cracow, 2005, Wolfgang Eyrich, University of Erlangen


Epiphany conference cracow 2005 wolfgang eyrich university of erlangen

Introduction

Chiral soliton model  antidecuplet including exotic states

D. Diakonov, V. Petrov, and M. Polyakov, Z. Phys. A 359 (1997) 305

m ~ 1530 MeV, Γ~ 15 MeV ,S = + 1, Jp = ½+

decayK0p + K+n

“anchor”  mass spacing

related width:Γ~ 50 MeV

Numerous calculations in various models:

different masses and widths, splitting, mixing  many questions!

Epiphany Conference, Cracow, 2005, Wolfgang Eyrich, University of Erlangen


Epiphany conference cracow 2005 wolfgang eyrich university of erlangen

Strangeness production at COSY-TOF: pN  KYN

Information: dynamics + structuredegrees of freedom

Meson Exchange Model

final state interaction

+

Search for exotic +

Introduction

different reaction channels : N = p, n Y = , o, +, -

Epiphany Conference, Cracow, 2005, Wolfgang Eyrich, University of Erlangen


Epiphany conference cracow 2005 wolfgang eyrich university of erlangen

Introduction

Strangeness production at COSY-TOF:

•exclusive observables

•full phase-space  Dalitz Plots

• polarization: Hyperon-polarization, polarized beam, (polarized target)

• threshold region  only few partial waves, no Y*

FSI

FSI

Epiphany Conference, Cracow, 2005, Wolfgang Eyrich, University of Erlangen


Epiphany conference cracow 2005 wolfgang eyrich university of erlangen

threshold

COSY limit

Introduction

Strangeness production

in pp  KYN reactions

before COSY:

almost no data

in threshold region

Epiphany Conference, Cracow, 2005, Wolfgang Eyrich, University of Erlangen


Epiphany conference cracow 2005 wolfgang eyrich university of erlangen

COSY - Facility

Cooler Synchrotron

Jülich

Circumference: 180 m

Phase space cooling:

electron and stochastic

Beam momentum:

maximum:3.6 GeV/c

TOF

Epiphany Conference, Cracow, 2005, Wolfgang Eyrich, University of Erlangen


Epiphany conference cracow 2005 wolfgang eyrich university of erlangen

COSY - beam

Beam-Quality

Veto-detector

with 2 mm hole

0.1% intensity

Beam-Intensity

used

1 - 3 x 107 p/s

Epiphany Conference, Cracow, 2005, Wolfgang Eyrich, University of Erlangen


Epiphany conference cracow 2005 wolfgang eyrich university of erlangen

COSY - TOF

large angle (non magnetic) spectrometer

modular vacuum vessel

tiny liquid hydrogen target

startdetector system

stopdetector system

Barrel Hodoscope

Ring Hodoscope

„Erlangen“ Startdetector

Neutron Detector

LH2Target

Beam

Central Hodoscope „Quirl“

3.4 m

Epiphany Conference, Cracow, 2005, Wolfgang Eyrich, University of Erlangen


Epiphany conference cracow 2005 wolfgang eyrich university of erlangen

COSY-TOF - Stop-Detector

TOF

„Quirl“

Epiphany Conference, Cracow, 2005, Wolfgang Eyrich, University of Erlangen


Epiphany conference cracow 2005 wolfgang eyrich university of erlangen

The „Erlangen Start Detector“

delayed decays of K0, Λ charged multiplicity 2  4  trigger

vertex reconstruction

identification of K0s:

decay  „V“

identification of Σ+:

decay  kink in track

complete geometric reconstruction

„4π“ cover

Epiphany Conference, Cracow, 2005, Wolfgang Eyrich, University of Erlangen


Epiphany conference cracow 2005 wolfgang eyrich university of erlangen

„Erlangen Start Detector“: Ring microstrip detector

Rearside 128 sectors

Frontside 100 rings

Epiphany Conference, Cracow, 2005, Wolfgang Eyrich, University of Erlangen


Epiphany conference cracow 2005 wolfgang eyrich university of erlangen

„Erlangen Start Detector“: Fibre Hodoscopes

Fibre

Hodoscope 1

Fibre

Hodoscope 2

Epiphany Conference, Cracow, 2005, Wolfgang Eyrich, University of Erlangen


Epiphany conference cracow 2005 wolfgang eyrich university of erlangen

Pbeam = 2.95 GeV/c Monte Carlo simulations

Q2

L  pp-

K0S p+p-

K0S p+p-

L  pp-

Q1

Q1+ 2

analysis cuts

pp Σ+K0p: background separation

Separation ofpp  pK0frompp  pK+and pK+S0( g L)

detector limits

Epiphany Conference, Cracow, 2005, Wolfgang Eyrich, University of Erlangen


Epiphany conference cracow 2005 wolfgang eyrich university of erlangen

pp Σ+K0p: reconstructed masses

Pbeam = 2.95 GeV/c

Runs 2000 + 2002

events

(GeV/c2)

K0 – mass

Σ+ - mass

(GeV/c2)

Epiphany Conference, Cracow, 2005, Wolfgang Eyrich, University of Erlangen


Epiphany conference cracow 2005 wolfgang eyrich university of erlangen

Pbeam = 2.95 GeV/c Run 2000 + Run 2002

Σ+

K0

Σ+

K0

939 events

939 events

pp Σ+K0p: cuts on masses

Epiphany Conference, Cracow, 2005, Wolfgang Eyrich, University of Erlangen


Epiphany conference cracow 2005 wolfgang eyrich university of erlangen

+

=

pp Σ+K0p: K0p mass spectra

Pbeam = 2.95 GeV/c

1.53

significance: 4 – 6 σ

(depending on method)

Epiphany Conference, Cracow, 2005, Wolfgang Eyrich, University of Erlangen


Epiphany conference cracow 2005 wolfgang eyrich university of erlangen

1.532

1.532

1.532

M2(K0p) in GeV2/c4

M2(K0p) in GeV2/c4

4.4 4.6 4.8 5.0 5.2 5.4

M2(K0Σ+) in GeV2/c4

M2(Σ+p) in GeV2/c4

pp Σ+K0p: Dalitz plots

Pbeam = 2.95 GeV/c

Epiphany Conference, Cracow, 2005, Wolfgang Eyrich, University of Erlangen


Epiphany conference cracow 2005 wolfgang eyrich university of erlangen

1.53

pp Σ+K0p: efficiency corrected K0p spectrum

Mass 1530 ± 5 MeV/c²

Width ≤ 18 ± 4 MeV/c² (FWHM)

Strangeness S = + 1

Cross section: 0.4 ± 0.1stat± 0.1sys µb

hep-ex/0403011, Phys. Lett. B 595 (2004), 127

Epiphany Conference, Cracow, 2005, Wolfgang Eyrich, University of Erlangen


Epiphany conference cracow 2005 wolfgang eyrich university of erlangen

Evidence forΘ+

Negativeresults especially from high energy experiments

Epiphany Conference, Cracow, 2005, Wolfgang Eyrich, University of Erlangen


Epiphany conference cracow 2005 wolfgang eyrich university of erlangen

New Results on LD2: Nakano et al. Pentaquark04

LEPS

1.53 GeV !

preliminary

Epiphany Conference, Cracow, 2005, Wolfgang Eyrich, University of Erlangen


Epiphany conference cracow 2005 wolfgang eyrich university of erlangen

COSY-TOF: Ongoing and new activities

In progress

Search for possible isospin partnersand

Investigation of N* resonances, especially width of N*(1710)

Experiment upgrade

2004: Fibre hodoscope with three layers

New Measurement

2004: pp Σ+K0p with much higher statistics

Independent Analyses

Epiphany Conference, Cracow, 2005, Wolfgang Eyrich, University of Erlangen


Epiphany conference cracow 2005 wolfgang eyrich university of erlangen

Pbeam : 2.95 GeV/c3.20 GeV/c3.30 GeV/c

1.532

1.532

1.532

related topic: Search for possible isospin partners

search for Ө++ : pp ΛK+p

Preliminary: no evidence for Ө++ in pK+ spectra

search for Ө+++ : pp  Ө+++

Epiphany Conference, Cracow, 2005, Wolfgang Eyrich, University of Erlangen


Epiphany conference cracow 2005 wolfgang eyrich university of erlangen

pp ΛK+p

1.712

1.712

2.5 3.0 3.5

m2(KЛ) GeV2/c4

related topic: width of N*(1710)resonance

Pbeam : 3.30 GeV/c

N*(1710) contributes strongly

Influence of pΛ-FSI

In progress: Investigation of Dalitz plots  width

Epiphany Conference, Cracow, 2005, Wolfgang Eyrich, University of Erlangen


Epiphany conference cracow 2005 wolfgang eyrich university of erlangen

Experiment upgrade

New fibre hodoscope with three layers

→increase of

efficiency

and purity

Two layers

Three layers

Epiphany Conference, Cracow, 2005, Wolfgang Eyrich, University of Erlangen


Epiphany conference cracow 2005 wolfgang eyrich university of erlangen

Measurement (Oct./Nov. 2004):pp → K0Σ+ p

Pbeam= 3.05 GeV/c

Estimate of output:

Reference: reaction channel pp → K+ Λ p

Preliminary analyses of 4 hours run: Λ missing mass

Expected overall gain for pp → K0Σ+ p: Factor of ~ 5 more events

compared to existing data (in agreement with the proposal)

Epiphany Conference, Cracow, 2005, Wolfgang Eyrich, University of Erlangen


Epiphany conference cracow 2005 wolfgang eyrich university of erlangen

Outlook

New results expected in the near future

confirmation of Θ+ !?  more insight

CLAS: high-statistics runs

(done, waiting for results)

HERMES: higher statistics

(done, waiting for results)

COSY-TOF: high-statistics run pp Σ+K0p

(done, waiting for results)

KEK E559: p+p →K-Q+ (run in May 2005)

Epiphany Conference, Cracow, 2005, Wolfgang Eyrich, University of Erlangen


Epiphany conference cracow 2005 wolfgang eyrich university of erlangen

Outlook COSY-TOF

In the positive case of Θ+ confirmation

Future measurements

2005: pn K0p using a LD2 target, successful tests in 2002/04

pol. beam + -polarization  towards parity of

2005/6: pp  Σ+K0p polarized beam + polarized targetparity

Experiment upgrade

2005/6: additional tracker

2005/6: polarized target

Epiphany Conference, Cracow, 2005, Wolfgang Eyrich, University of Erlangen


Epiphany conference cracow 2005 wolfgang eyrich university of erlangen

pn(p)  pK0Λ(p)

Unique signature:

2 „V‘s“ corresponding to

delayed decays

of Λ and K0

Epiphany Conference, Cracow, 2005, Wolfgang Eyrich, University of Erlangen


Epiphany conference cracow 2005 wolfgang eyrich university of erlangen

Pbeam = 2.95 GeV/c Run 2000 ↔ Run 2002

2000

K0

Σ+

2002

K0

K0

Σ+

pp Σ+K0p: reconstructed masses

Epiphany Conference, Cracow, 2005, Wolfgang Eyrich, University of Erlangen


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