Recent CDF results on heavy and exotic baryons in p-pbar collisions at ?s=1.96TeV

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Recent CDF results on heavy and exotic baryons in
p-pbar collisions at ?s1.96TeV
Francesca Curbis, Università di Roma La
Sapienza for CDF Collaboration
Baryons 04, 25-29 Oct, Palaiseau, France
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Outline

• Lb mass
• Lb lifetime
• Lb?Lcp
• Lb?pK,pp

• CDF detector
• Bottom baryons
• Pentaquark searches
• Conclusions

• theta plus
• exotic cascade
• theta c

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CDF detector _at_Tevatron
solenoid 1.4 T

• solenoid 1.4 T
• TRACKING system
• SILICON TRACKER
• (L00SVXISL)
• (up to ?2)
• DRIFT CHAMBER
• (96 layers) (?lt1)
• ? particle ID with dE/dx
• TIME OF FLIGHT?particle ID

large radius tracking wire chamber
time of flight
High mass resolution with CDF tracking system
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PID with TOF and dE/dx
TOF
dE/dx
complementary
K/p separation 1.16s
resolution 150ps for 150cm
Low momentum lt 1.6 GeV
high momentum gt 2 GeV
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Bottom baryons
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B mesons masses
world best
B B0 B0s Lb
Measurement using several exclusive decay modes
Use J/y trigger for detector calibration
Momentum scale, B-field correction and energy loss
m(Lb)56191.21.2 MeV/c2
compare to PDG 56249 MeV/c2
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Lb Lifetime in Lb ? J/yL
Lb only _at_Tevatron
Heavy Quark Expansion prediction _at_NLO
Worlds most precise measure in exclusive mode

• decay asymmetrically
• p very soft

Control sample B0 ? J/y K0s K0s long lived like L
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B0 ? J/y K0s high statistics
t (B0) 1.380.10ps
L b? J/yL
L b? J/yL
t (Lb) 1.250.260.10ps
compare to PDG value t (Lb) 1.2290.08ps
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Measurement of Lb ? Lcp
fbaryonxBr(Lb?Lcp)
eB0 x NLb x Br(D- ? Kpp)

0.660.110.090.18(Br)
fd x Br(B0 ? Dp)
eLb x NB0 x Br(Lc ? pKp)
FIRST OBSERVATION!
MC 1.200.020.11
Data 0.300.05 0.13
PDG 1.820.49
B0 ? D-p
B reflections
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Search for Lb?pK and pp decays
Previous best limit from ALEPH Br(Lb?pKpp)lt5010-
6 _at_90C.L.
Prediction Mohanta, Giri, Khanna 2001 Br(Lb?
pK)(1.4-1.9)10-6 Br(Lb? pp)(0.8-1.2)10-6 comp
are to Br(B0?Kp) 1810-6
Br(Lb?hh) lt 22 10-6 _at_90C.L.
Fully exclusive decay
N(Lb?hh) lt75 _at_90C.L.
Br(Lb? pKpp)lt22 10-6 _at_90C.L.
possibility for first observation of CP
asymmetry in baryons
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Pentaquark searches at CDF
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Motivation
prediction from Chiral Soliton Model (1997
Diakonov, Petrov, Polyakov)
new searches for 5-quark states
nK or pK0S
narrow resonances seen in several experiment
1530 MeV
1710 MeV
1890 MeV
2070 MeV
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Some pentaquark claims
LEPS 8 GeV Synchrotron g n ? KK-n reaction
NA49 pp collision at Ecm17.2GeV
H1 e-p collision at Ecm300GeV
Q ? n K
Qc ? Dp m309935MeV/c2 G 123 MeV
Exotic cascade m18622 MeV/c2 G lt 18 MeV
m1540105 MeV/c2 G lt 25 MeV
Q signal was confirmed by about 10 other
experiments
(CLAS, SAPHIR, ZEUS, HERMES, COSY-TOF,DIANA, SVD)
many observations, can CDF see these resonance?
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Q?p K0S ? ppp-
Q decays strongly ? zero lifetime ?use prompt
tracks prompt K0S
2 energy ranges ? 2 production mechanisms
Minbias Unbiased inelastic collisions
Jet20 Fragmentation from a 20 GeV jet
22.2M events
Higher yield
14.2M events
Lower BG
to remove L?pp- contamination m(pp) and m(pp) gt
1.13 GeV
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Selection of protons with TOF

• Measure
• Momentum p
• Time-of-flight t
• Pathlength L

calculate
Separation powerful at low momenta
Good PID in relevant momentum range
high purity selection protons 0.5ltpTlt2.1
GeV kaons 0.5ltpT lt1.3 GeV pions 0.5ltpT
lt1.3 GeV
Resolution ? 150ps _at_ 150 cm
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Known resonances
Combine two tracks (or trackKS) ? Calculate
invariant mass
f ? KK-
L(1520) ? pK-
K ? K0Sp
Opp charge Same charge
Reference mode
Two tracks with PID
Same topology
Acceptance limited by TOF cuts (determined with
MC)
Q ? K0Sp acceptance 1.5ltpTlt4.5 GeV
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Mass resolution
Data/MC agree on KS
MC resolution validated with K0S
s(Q)2.6MeV from MC compare with 15MeV expected
width
Detector resolution better than expected
intrinsic width
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pK0S invariant mass spectrum
Yields S18?56 Slt89 _at_90CL
Yields S-56?103 Slt76 _at_90CL
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Table of yields
Not corrected for acceptance-efficiency
Resonance statistics higher than any of the
Q?pK0S reports
High statistics reference signals ?, K, ?(1520)
No evidence of narrow resonance Q ? pK0S
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Exotic cascade X0,--3/2
X- long lived ct4.91 cm leaves hits in SVX
Hyperons tracked in silicon
X0,--3/2 ? X-p,-
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2-track trigger sample
Fit X0(1530) with BWxgaussian
mass15324 MeV/c2
Fit X(1860)
yield218292 events
yield4770 events
No signal
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Jet20 data
Fit X0(1530) with BWxG
mass15320.8 MeV/c2
Fit X(1860)
yield38734 events
yield-1627 events
No signal
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Q0c ? D()p
Reference channels
D(2460)
D0 (2460)
D ? D p
D ? D0p
? D p0
? D0p0
D ? D p-
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PID with TOF and dE/dx
PID cut optimized on independent calibration
sample
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Results
No narrow resonances
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Conclusions

• B-baryons
• Best measurement of LB mass
• Most precise LB lifetime in exclusive mode
• First observation of LB?J/yL
• Pentaquarks
• Despite good mass resolution, good particle
  identification and high statistic reference
  signals
• CDF do not see evidences for pentaquarks
• Plan to publish soon
• ?5Q needs high-statistics confirmation

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Backup slides
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Experimental signals
All signals in the 3-6 s range
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Reported signal peaks in nK
SAPHIR hep-ex0307083
CLAS hep-ex0307018
DIANA (hep-ex0304040)
CLAS-2 (hep-ex0402005)
LEPS (hep-ex0402005)
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Reported signal peaks in pK0S
COSY-TOF hep-ex0403011
Asratyan et al.hep-ex0309042
SVD hep-ex0401024
HERMES hep-ex0312044
ZEUS hep-ex0403051
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Negative evidences
HERA-B (hep-ex0403020)
BES (hep-ex0402012)
PHENIX (nucl-ex0404001)
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Reference modes from other experiments for Q
search
HERA-B
HERMES
SVD-2