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

Baryons04, 25-29 Oct, Palaiseau

Francesca Curbis - Università di Roma “La Sapienza” & INFN

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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



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Outline

CDF detector

Bottom baryons

Pentaquark searches

Conclusions

b mass

b lifetime

b→cp

b→pK,p

theta plus

exotic cascade

theta c



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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



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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



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Bottom baryons



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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



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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



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(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/



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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



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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



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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

1530 MeV

1710 MeV

1890 MeV

2070 MeV

narrow resonances seen in several experiment

qqqqq states



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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



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+→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



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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



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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



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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



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pK0S invariant mass

spectrum

YieldsS=1856

S<89 @90%CL

YieldsS=-56103

S<76 @90%CL



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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



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Exotic cascade 0,--3/2

Hyperons tracked in silicon

long lived c=4.91 cmleaves hits in SVX

→



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2-track trigger sample

Fit with BWxgaussian

yield=2182±92 events

mass=1532±4 MeV/c2 Fit

yield=47±70 eventsNo signal



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Jet20 data

yield=-16±27 events

Fit with BWxG mass=1532±0.8 MeV/c2

yield=387±34 events

Fit

No signal



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0c → D(*)p

Reference channels:

D** → D*+

→ D+ → D0

D** → D*0

D** → D*+

D*0 (2460)

D*+(2460)



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PID with TOF and dE/dx

PID cut optimized on independent calibration sample



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No narrow

resonances

c→D*-p c→D0pc→D-p

c→D0p

Results



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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



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Backup slides



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Experimental signals

All signals in the 3-6 range



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Reported signal peaks in nK+

SAPHIRhep-ex0307083

CLAS hep-ex0307018

DIANA (hep-ex0304040) LEPS (hep-ex0402005) CLAS-2 (hep-ex0402005)



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Reported signal peaks in pK0

S

HERMES hep-ex0312044

Asratyan et al.hep-ex0309042

SVD hep-ex0401024

ZEUS hep-ex0403051

COSY-TOF hep-ex0403011



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Negative evidencesHERA-B (hep-ex0403020)

PHENIX (nucl-ex0404001)

BES (hep-ex0402012)



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Reference modes from other experiments for +

searchHERA-B HERMES SVD-2

Documents

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