Cascades in COMPASS

Presented by G.BronaWarsaw University(gbrona@cern.ch)

On behalf of the COMPASS collaboration

Outline:1. COMPASS experiment in a muon programme2. Cascades spectroscopy in a muon programme3. COMPASS experiment in a hadron programme4. Plans and prospects for hadron spectroscopy5. Summary

Cascade Physics – A New Window On Baryon SpectroscopyJlab, Newport News, 1-3 December 2005

COmmonMuon and ProtonApparatus forStructure andSpectroscopy

LHC

SPS

COMPASS

1996 COMPASS Proposal 2001 Technical Run

2002, 2003, 2004 Data Taking (no data taking in 2005)Data Taking Foreseen till 2010

1996 2001 2002/03/04 2010

Grzegorz Brona – Cascade Physics – A New Window on Baryon Spectroscopy 1/27

Dubna (LPP and LNP), Moscow (INR, LPI, State University), Protvino

Warsaw (WU, SINS, TU)

Nagoya

Torino(University,INFN),

Trieste(University,INFN)

Bielefeld, Bochum, Bonn (ISKP & PI), Erlangen, Freiburg, Heidelberg, Mainz, München(LMU & TU)

Lisboa

Saclay

Burdwan, Calcutta

HelsinkiTel Aviv

Prague

CERN

The collaboration of ~250 physicists from 12 countries

Grzegorz Brona – Cascade Physics – A New Window on Baryon Spectroscopy 2/27

COMPASSProgramme with

muon beamProgramme with

hadron beam

Studies thatrequires pol. target

Studies that doesnot require pol. target

ρ productionΛpolarizationΞ pentaquarkΔG

A1Δq

TransverseLongitudinal

ΔqTSingle assymetries:Sivers, Collins

Primakoffeffect

Central production

Diffractivescattering

Spectroscopy

glueballs

hybrids

double-cbaryons

otherstates

2002, 20032004, 2006 2004, >2006

Grzegorz Brona – Cascade Physics – A New Window on Baryon Spectroscopy 3/27

Spectrometer setup and programme with the

muon beam

Grzegorz Brona – Cascade Physics – A New Window on Baryon Spectroscopy 4/27

SM1

SM2RICH1

Polarised Target

HCAL1

Muon Wall 1

Muon Wall 2,MWPC

μ beam Micromegas, SDC, Scifi

Straws, Gems

MWPC, Gems, Scifi

ECAL2HCAL2

Hodoscopes

Scifi, Silicon

Beam: 2 . 108 µ+/ spill (4.8s / 12s) Beam momentum: 160 GeV/cLuminosity: ~5 . 1032 cm-2 s-1 Beam polarization: -76%

Spectrometer for muon programme

Grzegorz Brona – Cascade Physics – A New Window on Baryon Spectroscopy 5/27

2003 setup

Spectrometer for muon programme

Grzegorz Brona – Cascade Physics – A New Window on Baryon Spectroscopy 6/27

2003 setup

LAS(>30 mrad, >0.4GeV/c)

SAS(<30 mrad, >4GeV/c)

μ+

two 60 cm long Target-Containerswith opposite polarization

superconductiveSolenoid (2.5 T)

3He – 4He Dilutionrefrigerator (T~50mK)

Dipole (0.5 T)

Target for muon programme

μ

6LiD in a solid stateOppositely polarized ~50%Spin reversal every 8h

vertex reconstruction

Acceptance: 2002-4 ±70 mrad>2006 ±180 mrad

Grzegorz Brona – Cascade Physics – A New Window on Baryon Spectroscopy 7/27

Ring Imaging CHerenkov Counter5 m5 m

6 m6 m3 m3 m

photon photon detectors:detectors:CsICsI MWPCMWPC

mirrormirrorwallwall

vesselvessel

radiatorradiator::CC44FF1010

• >80 m3 filled with C4F10• 116 VUV mirrors• 5.3 m2 photodetectors

82 944 pixels• >80k channels• π/K/p identification up to 50 GeV

from 2.5/9/17 GeVθθ(m

rad(m

rad))

p(GeV/cp(GeV/c))

pp

ππ oror μμ

KK

Grzegorz Brona – Cascade Physics – A New Window on Baryon Spectroscopy 8/27

Calorimetry

hadronshadrons

μμ

HCAL1:

%6.7%4.59⊕=

EEσ

for π

HCAL2:

%4%65⊕=

EEσ

for π

ECAL2:

%3.2%8.5⊕=

EEσ

Grzegorz Brona – Cascade Physics – A New Window on Baryon Spectroscopy 9/27

Particles identification

hadronshadrons

μμ

+ Muon filters and muon detectors at the end of SAS and LAS+ Magnets 1Tm and 4.4Tm – momenta measurment+ ECAL for neutral particles identification (e.g. π0→γγ)

RICH (π/K/p)HCAL (hadrons/μ)

Grzegorz Brona – Cascade Physics – A New Window on Baryon Spectroscopy 10/27

Examples of the reconstructed states

J/ψ→μμρ→ππ

φ→KK

p T[G

eV/c

]

−+

−+

+−

=LL

LL

PPPPα

Grzegorz Brona – Cascade Physics – A New Window on Baryon Spectroscopy 11/27

Weak decays reconstruction

For weak decays happening outside the target:• No multiple scattering• Less combinatorial background• Decays into two charged particles: K0→ ππ, Λ→pπ

Secondary vertices with 2-outgoing tracks + p/π mass assumption +|cosθΛπ|<0.9

Λ0: 1 250 000

Λ0: 640 000

2002-3 data

Grzegorz Brona – Cascade Physics – A New Window on Baryon Spectroscopy 12/27

Λ sample can be used as an input for Ξ reconstruction

Ξ(1321) reconstruction

π -

Ξ -Λ0

μ+ μ+’

γ*p

π -

XNN )1321(* −Ξ→→γμ

CDA<0.8 cmvertices hierarchyp.v. , Ξ- , Λ0

Ξ -: 17 900 events

Ξ +: 10 600 events (background substracted)

2002-3 data

Grzegorz Brona – Cascade Physics – A New Window on Baryon Spectroscopy 13/27

N

Reconstruction of the first excited state

π -

Ξ -Λ0

μ+ μ+’

γ*p

π -

π -

Ξ(1530)0: 1080 ± 90 events

Ξ(1530)0: 780 ± 80 events

Grzegorz Brona – Cascade Physics – A New Window on Baryon Spectroscopy 14/27

2002-3 data

N

Other possible resonances in Ξ(1321)πΞ(1620)

No Ξ(1820)Ξ(1950)

No other resonances visibleGrzegorz Brona – Cascade Physics – A New Window on Baryon Spectroscopy 15/27

2002-3 data

Ξ5 search

+++++++

+−−+−+−

−−−−−−−

→Λ→Ξ

→Λ→Ξ

→Λ→Ξ

ππππππ

ππππππ

ππππππ

p

pp

0

0

0

−++−+−+→Λ→Ξ ππππππ p

0

NA49(CERN): COMPASS:

Basing on the reconstructed Ξ(1321)search for Ξ5(1860) pentaquark

No signal found

Grzegorz Brona – Cascade Physics – A New Window on Baryon Spectroscopy 16/27

C. Alt et al., Phys. Rev. Lett. 92, 042003 (2004)

E.S. Ageev et al., EPJ C41, 469-474 (2005)

2002-3 data

Other possibilities for Ξ spectroscopy in COMPASS

• 2004 data will double 2002-3 statistics• further data will come in 2006

with larger hadron acceptance in the target• other channels can be studied:

o Ξ0(1530)πo ΛK

Grzegorz Brona – Cascade Physics – A New Window on Baryon Spectroscopy 17/27

Spectrometer setup and programme with the

hadron beam

Grzegorz Brona – Cascade Physics – A New Window on Baryon Spectroscopy 18/27

Spectrometer for hadron programme

Grzegorz Brona – Cascade Physics – A New Window on Baryon Spectroscopy 19/27

target: liquid hydrogenthin foils with different A

beam: π/K/p

New detectors planned:CEDARs, ECAL1, RPD,vertex detectornew tracking detectors

?

Doublecharmedbaryons

SU4 baryon multiplet

First evidence for ΞCC+ state SELEX (hadro-production):

+ΞCC++ΞCC

++Ξ*CC

FOCUS does not confirm (photo-production)

Grzegorz Brona – Cascade Physics – A New Window on Baryon Spectroscopy 20/27

M.Mattson et al., Phys.Rev.Lett. 89 (2002) 112001

S.Ratti Nucl.Phys.Proc.Suppl.115:33-36,2003

ΞCC reconstruction scheme

ΛC

ΞCC

π +K -

π +

K -p

Xpp CC+Ξ→

+−+Λ πKC

+−πpK

Optimistic (based on SELEX) estimation: >1000 ΞCC reconstructedpossible CCq spectroscopy

More conservative estimations: 100-170 ΞCC reconstructed100 effective days

280 GeV proton beam 108/spillThin targets of different A

Grzegorz Brona – Cascade Physics – A New Window on Baryon Spectroscopy 21/27

Vertex detector:

• 16 (or more) SI plates• Spaced by 2 mm• 10-15μm pitch

• Allows to reconstruct the charmdecay cascade

Decay detector:

• SI telescope• SCIFI, MicroMega detectors

• Vertex reconstruction

Tracks reconstruction

Grzegorz Brona – Cascade Physics – A New Window on Baryon Spectroscopy 22/27

Exotics

Glueballs - States with valence g, without valence qHybrids - States with non-trivial gluonic component4 quark states - qqqq statesPentaquarks - qqqqq states

Signature to look for: • exotic quantum numbers, eg. B=1,S=-2,Q=+1 for Ξ5(1860)• JPC not allowed for normal qq mesons e.q. 1-+

• Unusual branching ratios• Large production cross sections in gluon-rich processes

Grzegorz Brona – Cascade Physics – A New Window on Baryon Spectroscopy 23/27

Exotics 2

High statistics needed to measure partial widths,production mechanisms, PWA,glueball mixing etc.

Such high statistics feasible to obtain with COMPASS setup.

Experimental status: Possible candidates: glueballs (f0(1370),f0(1500), f0(1710))

hybrids (π1(1600))4-quarks (f1(1430)) pentaquarks (Θ+,Ξ5)

Grzegorz Brona – Cascade Physics – A New Window on Baryon Spectroscopy 24/27

Study of exotics in COMPASS

• 40 cm liquid hydrogen target • π/K or p beam will be used

• Central production of exotics:

The Recoil Particle Detector used for reconstruction and TOF measurement of large-angle tracks with low momenta:

RPD

target

vertex detector

The scintillator detector installedat the end of the setup register fast hadrons

Grzegorz Brona – Cascade Physics – A New Window on Baryon Spectroscopy 25/27

• Very good acceptance• High statistics• Access to higher mass states• Varying beam energy and particles type

COMPASS features during hadron run

• Different kinds of beam: π/K/p

• Different targets

• Vertex detector which allows to reconstruct short livingstates decaying in a secondary vertex

• Decay detector which allows to study in details the decay patterns

• Many additional tracking detectors improving globaltracking efficiency

Many features useful for Cascade physicsGrzegorz Brona – Cascade Physics – A New Window on Baryon Spectroscopy 26/27

Summary• COMPASS is running since 2002 in a muon mode• After 2006 hadron mode is foreseen• Present setup gives a possibility to study cascade hyperons

(Ξ(1320), Ξ(1530), other excited states, Ξ5(1860))• More data to come from 2004, 2006 years• Future setup will allow to perform accurate spectroscopy

at COMPASS- vertex and decay detectors- various hadron targets- various hadron beams - new trackers

• our most exciting spectroscopy aims are double charm and exotics, but there are also excellent opportunities for studies of cascade hyperons

Grzegorz Brona – Cascade Physics – A New Window on Baryon Spectroscopy 27/27