Transcript Document

HADRON
SPECTROSCOPY
AT
COMPASS
-- Exotic Hadrons at COMPASS -Takahiro Iwata
Yamagata University
on behalf of the COMPASS Collaboration
New Frontiers in QCD, February 5, 2010
OUTLINE
 Introduction to COMPASS
 Physics in Hadron Spectroscopy
 Diffractive dissociation to p-p-p+
 Diffractive dissociation to p-p0p0
 Central production of 4-charged-pions
 p-h, p-hh channels
 Kaonic final states: KKp, KK, Kp
 Conclusion
Takahiro Iwata
New Frontiers in QCD, February 5, 2010
COMPASS
NA58 experiment at CERN SPS
COmmon
Muon and
Proton
Apparatus for
Structure and
Spectroscopy
20 Institutes/11 counties/~230 physicists
Czech Republic, Finland, France, Germany, India, Israel, Italy, Japan,
Poland, Portugal and Russia
Bielefeld, Bochum, Bonn, Burdwan/Calcutta, CERN, Dubna, Erlangen,
Freiburg, Lisbon, Mainz, Moscow, Munich, Prage,
Protvino, Saclay, Tel Aviv, Torino, Trieste, Warsaw and Yamagata
Takahiro Iwata
New Frontiers in QCD, February 5, 2010
COMPASS at CERN
Lake LEMAN
COMPASS
Airport
LHC
SPS
CERN (France)
N
CERN (Suisse)
21/07/2015
Takahiro Iwata
BEACH08 26 june 2008
4
New Frontiers in QCD, February 5, 2010
PHYSICS PROGRAMS OF COMPASS
• Muon program
pol-m beam:
Runs: 2002-04,06-07
Nucleon Spin Structure
• Gluon polarization DG/G
• g1 spin structure function
• Flavor decomposition of
spin distributions
• Transverse spin effects
• Spin transfer in Lhyperon production
• Vector meson production
Takahiro Iwata
• Hadron program
hadorn-beams:
Runs : 2004, 08-09
Hadron spectroscopy
• Diffractive production
• Search for new exotic states,
glueballs or hybrids
• Light meson spectroscopy
Primakov scattering
• Polarizabilities
（Doubly charmed baryons）
New Frontiers in QCD, February 5, 2010
SETUP FOR MUON PROGRAM
An experiment with pol. muon beam and pol. target at CERN
two stages spectrometer
• Large Angle Spectrometer (SM1)
• Small Angle Spectrometer (SM2)
tracking, calorimetry, PID(RICH/muon-filter)
High rate capability
SciFi
Straws
Silicon
Micromegas SDC
MWPC E/HCAL
GEMs
W45
SM1
Polarized Target
MuonWall
SM2
E/HCAL
0.003 < x < 0.5
10-3 < Q2 < 10 GeV2
MuonWall
RICH
Pol.
m beam
160GeV/c
Pol. 80%
ｆrom SPS (CERN)
Takahiro Iwata
• high energy beam
• broad kinematical range
• large angular acceptance
NIM A 577(2007) 455
New Frontiers in QCD, February 5, 2010
SETUP FOR HADRON PROGRAM
Target: liquid H2, 40 cm long
(Pb in 2004 pilot run)
2008-09
Beam: 190 GeV positive/negative hadrons
Negative: 96% p-, 3.5% K-, 0.5% p-bar
Positive: 75% p, 25% p+, 5% K+
Beam intensity: 2·107/s ( 108/spill, spill=4.8s, cycle=16.8s)
P-id by beam Cherenkov Counter (CEDAR)
Takahiro Iwata
New Frontiers in QCD, February 5, 2010
TARGET PART IN HADRON PROGRAM
RPD(Recoil Proton Detector)
Installed in 2007
Takahiro Iwata
New Frontiers in QCD, February 5, 2010
Physics
in
Hadron
Spectroscopy
Takahiro Iwata
New Frontiers in QCD, February 5, 2010
PHYSICS GOALS
• Objectives mainly in meson spectroscopy
• QCD allows states which are forbidden in the
quark Model
• Exotic states
• Glueballs:
• Hybrids :
• Tetraquarks :
• Mixing with ordinary mesons with the same
quantum numbers  complicated situation
• Exotic JPC states :
 non-qq states : important to find them
COMPASS contributes in the low mass region
Takahiro Iwata
New Frontiers in QCD, February 5, 2010
GLUEBALLS
Quenched L-QCD prediction
Lightest glueballs:
scalar
tensor
Experimental candidate:
• f0(1500) (Crystal Barrel, WA102)
JPC = 0++ << ordinary JPC
 mixing with ordinary mesons!
 COMPASS
[Y. Chen et al., Phys. Rev. D 73, 014516 (2006)]
Takahiro Iwata
New Frontiers in QCD, February 5, 2010
HYBRIDS
Light meson sector
hybrid candidate with exotics JPC=1-+:
• p1(1400) (VES, E852, Crystal Barrel)
• p1(1600) (E852, VES)
35 waves
20 waves
Events / 0.04 GeV/c2
still controversial...
[A.R. Dzierba et al., PRD 73, 072001 (2006)]
M(3p) (GeV/c2)
[S.U. Chung et al., PRD 65, 072001 (2002)]
Takahiro Iwata
 COMPASS
New Frontiers in QCD, February 5, 2010
PRODUCTION MECHANISMS
Central production
• Rapidity gap between pslow, hfast, X
• Beam particle looses ~10% of its energy
• Particles at large angles from X decays
• Possible source of glueballs
Takahiro Iwata
Diffractive dissociation
• in forward direction
• separate particles at
very small angles
• Production of Isovectors
• study hybrid states
New Frontiers in QCD, February 5, 2010
Diffractive
Dissociation
to
- +
p p p final State
Takahiro Iwata
New Frontiers in QCD, February 5, 2010
p -p -p + IN 2004
•
•
•
•
•
•
Pilot run in 2004 ( 3 days )
190 GeV p- beam
3mm thick Pb target
Diffractive dissociation from pPomeron exchange
p- p- p+ final state (4 M events)
Takahiro Iwata
New Frontiers in QCD, February 5, 2010
INVARIANT MASS OF 3p system 2004
COMPASS
BNL E852
Pp=18 GeV/c
250 k events
0.08<t’<1.0 GeV2/c2
450 k events
0.1<t’<1.0 GeV2/c2
BNL E852
COMPASS
Acceptance
COMPASS acceptance is flat 50-60%, independent from the mass
Takahiro Iwata
New Frontiers in QCD, February 5, 2010
PARTIAL WAVE ANALYSIS
Illinois/Protovino/Munich Program &
BNL/Munich Program (independent cross-check)
based on Isobar model
Step 1. Mass-Independent PWA
• 40 MeV/c2 mass bin
• Gottfried-Jackson frame ( z//beam )
• 42 partial waves: JPCMe Y L
Y
:isobars (pp)S, f0(980), r(770), f2(1270), r3(1690)
• Background wave
• fit in extended maximum likelihood
Step 2. Mass-Dependent c2 fit
• fit the results of step 1
M: absolute value of the spin
projection to the z axis
• Parameterized by Breit-Wigner
• 6 waves + coherent background
Takahiro Iwata
New Frontiers in QCD, February 5, 2010
MAJOR WAVES
Takahiro Iwata
New Frontiers in QCD, February 5, 2010
JPC=1- + EXOTIC WAVE
p1(1600): 1-+
1-+ phase to 1++
p1(1600): 1-+
a1(1260): 1++
1-+ phase to 2-+
p2(1670): 2-+
p1(1600): 1-+
Non-resonant B.G.
due to Deck-effect
Phys. Rev. Lett. 13, 169 (1964).
Submitted to Phys.Rev. Lett.
Takahiro Iwata
p -p - p +
IN 2008
190 GeV/c negative hadron beam;
P-id by beam line Cherenkov Counter
 96% p-, 3.5% K-, 0.5% p-bar
40 cm liquid hydrogen target
Spectrometer upgrade before 2008 run
RPD, Silicon, Pixel GEM
X10 BNL E852 statistics for full 2008 data
Exclusive measurements
Exclusivity cut
[180-190 GeV]
After all cuts
Takahiro Iwata
New Frontiers in QCD, February 5, 2010
PWA FOR 2008 p -p -p +
PWA has been started
Illinois/Protovino/Munich Program.
Same wave set (42 waves) .
No acceptance correction applied yet.
2++ total(e=+)
Dominant waves
2-+ total(e=+)
1++ total(e=+)
Takahiro Iwata
New Frontiers in QCD, February 5, 2010
Diffractive
Dissociation
to
0 0
p p p final State
Takahiro Iwata
New Frontiers in QCD, February 5, 2010
p -p 0 p 0
IN 2008
Isospin partner to p-p-p+
Consistency check
Different isobars in decay chain
Takahiro Iwata
New Frontiers in QCD, February 5, 2010
1ST ATTEMPT OF PWA FOR p - p 0
PWA : Illinois/Protovino/Munich Program
Isobars:
p0
2++r p
a2(1280)
No acceptance correction applied yet.
Relative intensities of charged and neutral
modes are consistent with the isobar decays
Intensities
1++r p
2-+ f2 p
Br  r -  p - + p 0 
a1(1260)
p2(1670)
normalized
to a2
Br  r 0  p + + p - 
Br  f 2  p 0 + p 0 
Br  f 2  p + + p - 
Takahiro Iwata
1

1
2
New Frontiers in QCD, February 5, 2010
Central Production of
4-charged-pions
–
–
+ - + p pp fast p p p p p)
Takahiro Iwata
New Frontiers in QCD, February 5, 2010
p p p p IN CP
+
-
+
-
p – pp –fast (p + p - p + p – ) pslow
Study glueballs ( f0 and f2 families)
pX
p
p-fast
p- +
p+
pp
pslow
Central Production( CP)
Takahiro Iwata
New Frontiers in QCD, February 5, 2010
ENHANCEMENT OF CP
Enhancing CP with Feynman X:
COMPASS
0++rr ?
WA102
f1(1285)
f0(1450)
f2(1900)
f1  p+p-h
p+p-p+p- (p0)
h’  p+p-h
p+p-p+p- (p0)
PWA is prepared in COMPASS
WA102 (Phys.Lett.B413:217-224,1997)
Takahiro Iwata
New Frontiers in QCD, February 5, 2010
p pp h p,
–
–
p pp hh p
–
Takahiro Iwata
–
New Frontiers in QCD, February 5, 2010
p -h
CHANNEL
p – p p – h p
( 2g )
h event selection
450  mg1g 2  650 MeV
Constraint 1 h with
confidence level > 10%
• exotic Jpc=1-+ , p1(1400) ph ?
p-h
p1(1400) ?
• Amplitude analysis with 150k
events in progress
• Better statistics expected with
calorimeter calibration(2008 data)
and LASER and LED monitor
(2009 data)
Takahiro Iwata
New Frontiers in QCD, February 5, 2010
p - hh
CHANNEL
p – p p – h h p
( 4g )
p0 background
rejected
hh event selection
m
g 1g 2
- mh
 + m
2
g 3g 4
- mh

2
 25MeV
Fit on two h mass constraint:
confidence level > 10% ( for each combination)
Hybrid ?
3 combinations / event
Projection
Takahiro Iwata
p-hh
New Frontiers in QCD, February 5, 2010
p - h and hh IN p - hh
CHANNEL
-
p h
p1(1400); exotic Jpc state
• exotic Jpc=1-+ , p1(1400) ph
• glueball candidate f0(1500) hh
• Structure at 1.5GeV in hh
:glueball ?
• Amplitude analysis with 5k
events for ph and hh in progress
• Better statistics expected with
calorimeter calibration(2008 data)
and LASER and LED monitor
(2009 data)
Takahiro Iwata
hh
hh
New Frontiers in QCD, February 5, 2010
Kaonic Final States:
+ – –
–
p p K K p p,
0 0 –
–
p p Ks Ks p p,
….
Takahiro Iwata
New Frontiers in QCD, February 5, 2010
KAONIC FINAL STATES
Glueball candidates decaying into KK
f0(1380),f0(1500): qq mixing with gg ?
• Hybrid candidates decaying into KKp
p(1800): usual 31S0 or Hybrid?
Accessible channels:
+ – –
–
p pK K p p,  This talk
p – p Ks0Ks0 p – p,  This talk
–
– – +
K p K p p p,
p – p Ks0KL0 p – p,
….
same with positive charged beam
Takahiro Iwata
New Frontiers in QCD, February 5, 2010
KK SUBSYSTEM
Allowed Jpc for different combinations of KK
+
-
K K identified by RICH:
10 GeV/c < PK < 30 GeV/c
 Cut in acceptance
RICH
 Neutral channels pick out the subsets
Event selection
Ks0Ks0
K +K
–
range
for kaon-id.
Two displaced vertexes for Ks
• 3 charged (+--) tracks
• One negative track identified as K- by RICH
Takahiro Iwata
New Frontiers in QCD, February 5, 2010
Kp INVARIANT MASS
• Expected structures for
K*(892): 13S1
K*(1410):23S1,
K0*(1430):13P0 ,
K2*(1430): 11D2
K +p -
• Acceptance in the low mass region
is affected by RICH threshold.
• p contamination in P-id
Ks0p
Takahiro Iwata
-
• Almost background free
• the structures are also visible.
New Frontiers in QCD, February 5, 2010
KK INVARIANT MASS
K+K-
• Known resonances visible in
both mass spectra:
f0(1500): glueball candidate
f2‘(1520): 13P2
Ks0 Ks0
Takahiro Iwata
New Frontiers in QCD, February 5, 2010
KKp INVARIANT MASS
K + K -p • Structures around
1.8 GeV and 2.2GeV
Ks0 Ks0 p -
Takahiro Iwata
New Frontiers in QCD, February 5, 2010
Kp v.s. KKp in K+K-p -
X(2.2GeV)K *(890)+ K - / Kp1400-1500 + K X(1.8GeV)K *(890)+ K -
Takahiro Iwata
New Frontiers in QCD, February 5, 2010
Kp v.s. KKp in Ks Ks p -
X(2.2GeV)K *(890)+ Ks / Kp1400-1500 + Ks
X(1.7GeV)K *(890)+ Ks
Takahiro Iwata
New Frontiers in QCD, February 5, 2010
KK v.s. KKp in
- +
K Kp
X(2.2GeV) (f /a0/f0) + p –
 KK1600  + p X(1.8GeV)KK1500 + p -
Takahiro Iwata
New Frontiers in QCD, February 5, 2010
KK v.s. KKp in Ks Ks p a0(980)/f0(980)
m(Ks0 Ks0p-) /GeV
Quite different form K+K-p- due to
allowed JPC=0++,2++,4++ for KsKs
f0(1500)
f0(1380)
m(Ks0 Ks0)/GeV
Takahiro Iwata
New Frontiers in QCD, February 5, 2010
NEXT STEPS IN KKp CHANNELS
• Mass-independent PWA to be performed
• Enhancing central production for KK system
FASTEST-p
Selection
Ks0 Ks0
Takahiro Iwata
Ks0 Ks0
New Frontiers in QCD, February 5, 2010
CONCLUSION
• COMPASS is a multi-purpose spectrometer
• Muon program for nucleon spin structure
• Hadron program mainly for hadron spectroscopy
• COMPASS has started studies on spectroscopy
• VERY high statistics ( partly > 200 times previous work)
• More refined PWA is underway
Status:
• Exotic 1-+ p1(1600) has been observed in p-p-p+ channel
• The 3p neutral mode shows consistent signals
• centrally produced charged 4p analysis is ongoing
• p-h, p-hh analysis is ongoing
• Analysis with kaonic channels is ongoing
• Interesting structures observed in KKp channels
Takahiro Iwata
New Frontiers in QCD, February 5, 2010
Backup Slides
Takahiro Iwata
New Frontiers in QCD, February 5, 2010
WAVE SETS IN PWA OF 2004 DATA
Takahiro Iwata
New Frontiers in QCD, February 5, 2010
0-+ : p(1800) IN 2004 PWA
• Constant width BW for p(1800)
• With low mass background
Takahiro Iwata
New Frontiers in QCD, February 5, 2010
p- multi-g CHANNELS
Selection of p- n-g (n=2, n=4) events
1 outgoing negative track with Etrack < 180 GeV
n=2 and n=4 good clusters in ECAL1 and ECAL2
Energy balance: 180 < E p ng <200 GeV assuming the track to be a pion
Co-planarity : -0.3 < fpng – fp < 0.3 rad.
Takahiro Iwata
New Frontiers in QCD, February 5, 2010
THE RICH DETECTOR
5m
photon
detectors
C4F10
• radiator gas:
C4F10
20 m2 surface
• mirror wall:
• photon-detectors:
•outer part (75%) MWPC(pad RO) with CsI cathode
• inner part(25%) 576 MAPMTs with indiv. telescope
threshold momenta
● p = 2 GeV/c
p
● p = 9 GeV/c
K
● p =17 GeV/c
P
Takahiro Iwata
Installed in 2005,
Used in data taking from 2006
New Frontiers in QCD, February 5, 2010