Baryons04, 25-29 Oct, Palaiseau
Francesca Curbis - Università di Roma “La Sapienza” & INFN
1
Recent CDF results on heavy and exotic baryons
in p-pbar collisions at s=1.96TeV
Francesca Curbis,
Università di Roma “La Sapienza”
for CDF Collaboration
Baryons 04, 25-29 Oct, Palaiseau, France
Baryons04, 25-29 Oct, Palaiseau
Francesca Curbis - Università di Roma “La Sapienza” & INFN
2
Outline
CDF detector
Bottom baryons
Pentaquark searches
Conclusions
b mass
b lifetime
b→cp
b→pK,p
theta plus
exotic cascade
theta c
Baryons04, 25-29 Oct, Palaiseau
Francesca Curbis - Università di Roma “La Sapienza” & INFN
3
CDF detector @Tevatron
large radius tracking wire
chamber
time of flight
High mass resolution with CDF tracking system
solenoid 1.4 T
TRACKING system:
• SILICON TRACKER
(L00+SVX+ISL)
(up to ||~2)
• DRIFT CHAMBER
(96 layers) (||<1)
→ particle ID with dE/dx
TIME OF FLIGHT→particle ID
solenoid 1.4 T
Baryons04, 25-29 Oct, Palaiseau
Francesca Curbis - Università di Roma “La Sapienza” & INFN
4
PID with TOF and dE/dx
resolution 150ps for 150cm
TOF dE/dx
Low momentum < 1.6 GeV
K/separation 1.16
high momentum > 2 GeV
complementary
Baryons04, 25-29 Oct, Palaiseau
Francesca Curbis - Università di Roma “La Sapienza” & INFN
5
Bottom baryons
Baryons04, 25-29 Oct, Palaiseau
Francesca Curbis - Università di Roma “La Sapienza” & INFN
6
B mesons masses B+ B0 B0
s b
world best
m(b)=5619±1.2±1.2 MeV/c2
compare to PDG
5624±9 MeV/c2
Measurement using several exclusive decay modes
Use J/trigger for detector calibration: Momentum scale, B-field correction and energy loss
Baryons04, 25-29 Oct, Palaiseau
Francesca Curbis - Università di Roma “La Sapienza” & INFN
7
b Lifetime in b→J/
World’s most precise measure in exclusive mode
decay asymmetrically
very soft
b only @Tevatron
Heavy Quark Expansion
prediction @NLO (b)
(B0)= 0.87±0.05
(Hep-ph 0407004)
Control sample: B0 →
J/K0s
K0s long lived like
Baryons04, 25-29 Oct, Palaiseau
Francesca Curbis - Università di Roma “La Sapienza” & INFN
8
(b)= 1.25±0.26±0.10ps
B0 → J/K0s
high statistics
(B0)= 1.38±0.10ps
compare to PDG value (b)= 1.229±0.08ps
b→ J/
b→ J/
Baryons04, 25-29 Oct, Palaiseau
Francesca Curbis - Università di Roma “La Sapienza” & INFN
9
Measurement of b → cfbaryonxBrb→+
c
fd x BrB0
→D+
=
Data: 0.30±0.05 ±0.13
MC: 1.20±0.02±0.11
PDG: 1.82±0.49
= 0.66±0.11±0.09±0.18(Br) FIRST OBSERVATION!
b x NB0 x Br+c
→pK
B0 x Nb x BrD- →K
B0 → D-
B reflections
Baryons04, 25-29 Oct, Palaiseau
Francesca Curbis - Università di Roma “La Sapienza” & INFN
10
Search for b→pK and pdecays
N(b→hh)
B x fB x Br(B0→K)=
x f x Br(b→hh)
N(B0→K)
Nb→hh<75 @90%C.L.
Brb→hh< 22 10-6
@90%C.L.
Prediction: Mohanta, Giri, Khanna 2001
Br(b→ pK)=(1.4-1.9)×10-6
Br(b→p)=(0.8-1.2)×10-6
compare to Br(B0→K)= 18×10-6
Br(b→ pK+p)<22× 10-6 @90%C.L.
Previous best limit from ALEPH
Br(b→pK+p)<50×10-6 @90%C.L.
possibility for first observation of CP
asymmetry in baryons
Fully exclusive decay
Baryons04, 25-29 Oct, Palaiseau
Francesca Curbis - Università di Roma “La Sapienza” & INFN
11
Pentaquark searches at CDF
Baryons04, 25-29 Oct, Palaiseau
Francesca Curbis - Università di Roma “La Sapienza” & INFN
12
Motivation
prediction from Chiral Soliton Model (1997 Diakonov, Petrov, Polyakov)new searches for 5-quark states
nK+ or pK0S
1530 MeV
1710 MeV
1890 MeV
2070 MeV
narrow resonances seen in several experiment
qqqqq states
Baryons04, 25-29 Oct, Palaiseau
Francesca Curbis - Università di Roma “La Sapienza” & INFN
13
c → D*+p
m=3099±3±5MeV/c2
=12±3 MeV
Exotic cascade
m=1862±2 MeV/c2
< 18 MeV
LEPS 8 GeV Synchrotron n → K+K-n reaction
m=1540±10±5 MeV/c2
< 25 MeV
many observations, can CDF see these resonance?
NA49 pp collision at Ecm=17.2GeV
H1 e-p collision at Ecm=300GeV
→ n K+
signal was confirmed by about 10 other experiments
(CLAS, SAPHIR, ZEUS, HERMES, COSY-TOF,DIANA, SVD)
Some pentaquark claims
Baryons04, 25-29 Oct, Palaiseau
Francesca Curbis - Università di Roma “La Sapienza” & INFN
14
+→p K0S → p+-
2 energy ranges → 2 production mechanisms
+ decays strongly → zero lifetime →use prompt tracks + prompt K0
S
22.2M events
14.2M events
to remove →p- contamination: m(p) and m(p) > 1.13 GeV
Minbias
Unbiased
inelastic
collisions
Jet20
Fragmentation
from a 20 GeV jet
Lower BG
Higher yield
Baryons04, 25-29 Oct, Palaiseau
Francesca Curbis - Università di Roma “La Sapienza” & INFN
15
Selection of protons with TOF
high purity selectionprotons 0.5<pT<2.1
GeVkaons 0.5<pT <1.3 GeVpions 0.5<pT <1.3
GeV
Resolution 150ps @ 150 cm
Separation powerful at low momenta
Measure:•Momentum p•Time-of-flight t•Pathlength L
calculate
Good PID in relevant
momentum range
Baryons04, 25-29 Oct, Palaiseau
Francesca Curbis - Università di Roma “La Sapienza” & INFN
16
Known resonances
Opp chargeSame charge
→K+K- 1520) → pK- K*+ → K0S+
Acceptance limited by TOF cuts:
(determined with MC)+ → K0
Sp acceptance: 1.5<pT<4.5 GeV
Combine two tracks (or track+KS) → Calculate invariant mass
Two tracks with PID Reference mode Same topology
Baryons04, 25-29 Oct, Palaiseau
Francesca Curbis - Università di Roma “La Sapienza” & INFN
17
Mass resolution
+)=2.6MeV from MCcompare with 15MeV expected width
MC resolution validated with K0
S
Data/MC agree on KS
Detector resolution better
than expected intrinsic width
Baryons04, 25-29 Oct, Palaiseau
Francesca Curbis - Università di Roma “La Sapienza” & INFN
18
pK0S invariant mass
spectrum
YieldsS=1856
S<89 @90%CL
YieldsS=-56103
S<76 @90%CL
Baryons04, 25-29 Oct, Palaiseau
Francesca Curbis - Università di Roma “La Sapienza” & INFN
19
Not corrected for acceptance-efficiency
Minbias data Jet20 data
K+K-
1520) pK-
K*+ K0S+
+ pK0S
limit on +
@90%CL
19,721273
3,276327
15,695775
1856
<89
26,658385
4,915702
35,7691,390
-56103
<76
No evidence of narrow resonance
→ pK0S
High statistics reference signals , K*+, (1520)
Resonance statistics higher than any of the +→pK0S
reports
Table of yields
Baryons04, 25-29 Oct, Palaiseau
Francesca Curbis - Università di Roma “La Sapienza” & INFN
20
Exotic cascade 0,--3/2
Hyperons tracked in silicon
long lived c=4.91 cmleaves hits in SVX
→
Baryons04, 25-29 Oct, Palaiseau
Francesca Curbis - Università di Roma “La Sapienza” & INFN
21
2-track trigger sample
Fit with BWxgaussian
yield=2182±92 events
mass=1532±4 MeV/c2 Fit
yield=47±70 eventsNo signal
Baryons04, 25-29 Oct, Palaiseau
Francesca Curbis - Università di Roma “La Sapienza” & INFN
22
Jet20 data
yield=-16±27 events
Fit with BWxG mass=1532±0.8 MeV/c2
yield=387±34 events
Fit
No signal
Baryons04, 25-29 Oct, Palaiseau
Francesca Curbis - Università di Roma “La Sapienza” & INFN
23
0c → D(*)p
Reference channels:
D** → D*+
→ D+ → D0
D** → D*0
D** → D*+
D*0 (2460)
D*+(2460)
Baryons04, 25-29 Oct, Palaiseau
Francesca Curbis - Università di Roma “La Sapienza” & INFN
24
PID with TOF and dE/dx
PID cut optimized on independent calibration sample
Baryons04, 25-29 Oct, Palaiseau
Francesca Curbis - Università di Roma “La Sapienza” & INFN
25
No narrow
resonances
c→D*-p c→D0pc→D-p
c→D0p
Results
Baryons04, 25-29 Oct, Palaiseau
Francesca Curbis - Università di Roma “La Sapienza” & INFN
26
Conclusions• B-baryons :
Best measurement of B mass
Most precise B lifetime in exclusive mode
First observation of B→J/
• 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
Baryons04, 25-29 Oct, Palaiseau
Francesca Curbis - Università di Roma “La Sapienza” & INFN
27
Backup slides
Baryons04, 25-29 Oct, Palaiseau
Francesca Curbis - Università di Roma “La Sapienza” & INFN
28
Experimental signals
All signals in the 3-6 range
Baryons04, 25-29 Oct, Palaiseau
Francesca Curbis - Università di Roma “La Sapienza” & INFN
29
Reported signal peaks in nK+
SAPHIRhep-ex0307083
CLAS hep-ex0307018
DIANA (hep-ex0304040) LEPS (hep-ex0402005) CLAS-2 (hep-ex0402005)
Baryons04, 25-29 Oct, Palaiseau
Francesca Curbis - Università di Roma “La Sapienza” & INFN
30
Reported signal peaks in pK0
S
HERMES hep-ex0312044
Asratyan et al.hep-ex0309042
SVD hep-ex0401024
ZEUS hep-ex0403051
COSY-TOF hep-ex0403011
Baryons04, 25-29 Oct, Palaiseau
Francesca Curbis - Università di Roma “La Sapienza” & INFN
31
Negative evidencesHERA-B (hep-ex0403020)
PHENIX (nucl-ex0404001)
BES (hep-ex0402012)
Baryons04, 25-29 Oct, Palaiseau
Francesca Curbis - Università di Roma “La Sapienza” & INFN
32
Reference modes from other experiments for +
searchHERA-B HERMES SVD-2