b physics at the tevatron
DESCRIPTION
B physics at the Tevatron. UK HEP Forum “ From the Tevatron to the LHC ” The Cosener's House, Abingdon,UK April 24-25, 2004 Rick Jesik Imperial College London Representing the D Ø and CDF collaborations. at 2 TeV. at Z 0. at (4S). B physics at hadron colliders. Pros - PowerPoint PPT PresentationTRANSCRIPT
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B physics at the TevatronB physics at the Tevatron B physics at the TevatronB physics at the Tevatron
UK HEP Forum“From the Tevatron to the LHC”The Cosener's House, Abingdon,UK
April 24-25, 2004
Rick Jesik Imperial College LondonRepresenting the DØ and CDF
collaborations
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B physics at hadron collidersB physics at hadron collidersB physics at hadron collidersB physics at hadron colliders
Pros– Large production cross
section– All b species produced
B, B0, Bs, Bc, b, b
Cons– Inelastic cross section is a
factor of 103 larger with roughly the same pT spectrum
– Many decays of interest have BR’s of the order 10-6
– Large combinatorics and messy events
μb150)bbp(p
nbBBee 1)(
nb7)bbee(
at 2 TeV
at (4S)
at Z0
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The CDF Run II detectorThe CDF Run II detectorThe CDF Run II detectorThe CDF Run II detector
The CDF detector has undergone extensive upgrades
– New silicon vertex detector inner layer at 1.35 cm
– New central tracker– Extended coverage– Time of flight detector– Second level impact
parameter trigger Allows all hadronic
b triggers
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The DØ Run II detectorThe DØ Run II detectorThe DØ Run II detectorThe DØ Run II detector
The DØ detector has undergone very extensive upgrades
– Silicon vertex detector || < 3.0
– Central fiber tracker and pre-shower detectors
– 2 T solenoid magnet– Low pT central muon
trigger scintilators– New forward system– L2 silicon track trigger
commissioning now
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DDØ extendedØ extended tracking coverage tracking coverageDDØ extendedØ extended tracking coverage tracking coverage
|| for kaons from D*D0pT spectrum of soft pion from D*D0
Tracks are reconstructed• over a wide range • starting from pT = 200 MeV
Data from semileptonic decays (B D X)
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B triggers at the TevatronB triggers at the TevatronB triggers at the TevatronB triggers at the Tevatron
Dimuons – pT> 1.5 - 3.0 GeV – CDF central, DØ out to eta of 2
Single muons– DØ: very pure central track matched muons with
pT > 4 GeV, presence of additional tracks used at medium lums, impact parameters only used at high lums
– CDF: pT > 4 GeV/c, 120 m < d0(Trk) < 1mm, pT(Trk) > 2 GeV/c
Two displaced vertex tracks - hadronic sample– CDF: pT(Trk) >2 GeV/c, 120 m < d0(Trk) < 1mm,
pT > 5.5 GeV/c
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Hadroproduction of heavy quarksHadroproduction of heavy quarksHadroproduction of heavy quarksHadroproduction of heavy quarks
NLO processes contribute with the same magnitude as LO ones
Lead to different kinematic correlations– R, , pT1 vs. pT2
R.D. Field - hep-ph/0201112
flavor creation flavor excitation gluon splitting
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bb--quark cross sections at the Tevatronquark cross sections at the Tevatronbb--quark cross sections at the Tevatronquark cross sections at the Tevatron
Run 1 measured x-sections were a factor of two or three higher than the central values of the theory at the time.
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Large uncertainties Large uncertainties Large uncertainties Large uncertainties
Experimental uncertainties– We don’t measure b-quarks, only B-hadrons
Fragmentation uncertainty – Peterson is not correct
– B decay products often not fully reconstructed Must extrapolate to B-hadron, then b-quark pT
Theoretical uncertainties– hard scatter really needs NNLO – scale factors (x2)– quark mass (10%), PDF’s (20%)– kT effects and fragmentation
Correlations between the above often not included in theory vs. experiment comparisons– Was this merely a 2 discrepancy? – or more?
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An exotic explanationAn exotic explanationAn exotic explanationAn exotic explanation
SUSY gluino production and decay to b-quarks– Berger, Tait, Wagner
Also produce like sign BB hadrons and influence mixing measurements
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Improvements in theoryImprovements in theoryImprovements in theoryImprovements in theory
New LO and NLO B-meson fragmentation functions determined from recent data – Binnewies, Kniehl, Kramer
Next to leading log resumation and re-tuned frag. functions: FONLL– Cacciari, Nason
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Open charm cross sectionsOpen charm cross sections Open charm cross sectionsOpen charm cross sections
Charm production probes the same hard scatter processes as beauty, but has different fragmentation – good cross check of theory
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Open charm cross sectionsOpen charm cross sections Open charm cross sectionsOpen charm cross sections
Same level of agreement or disagreement between data and theory (FONLL) as for beauty
D0D0 (pT≥5.5)
13.3±0.2±1.5 b
D+ (pT≥6) 4.3±0.1±0.7 b
D*+ (pT≥6)
5.2±0.1±0.8 b
Ds+ (pT≥8)
0.75±0.05±0.22 b
K
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Inclusive Inclusive JJ// cross section cross section Inclusive Inclusive JJ// cross section cross section
CDF’s new muon trigger capabilities extend the J/ pT acceptance down to 0 – was 5 GeV in Run I.
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Differential B Differential B J/J/cross sectioncross section Differential B Differential B J/J/cross sectioncross section
b-hadron x-section d/dpT(Hb)
Assume a b-hadron pT spectrum
Unfold pT(Hb) from pT(J/) using MC
New b-hadron pT spectrum
Iterate to obtain the correct pT spectrum
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Differential dDifferential d/dp/dpTT(B) as function of p(B) as function of pTT(B)(B) Differential dDifferential d/dp/dpTT(B) as function of p(B) as function of pTT(B)(B) (ppB, |y|<0.6) * BR(B J/) * BR(J/+-) = 24.5 0.5(stat) 4.7(syst) nb
(ppb, |y|<0.6) =
18.0 0.4 3.8
b
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Comparison to theoryComparison to theoryComparison to theoryComparison to theory
FONLL, a la Cacciari, Frixione, Mangano, Nason, Ridolfi
Impressive agreement with new data!
But… the measured inclusive x-section is at the same level as the Run I exclusive one – it should be 10-15% higher, due to the increase in beam energy.
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Fully reconstructed B’sFully reconstructed B’s Fully reconstructed B’sFully reconstructed B’s
Better for cross section measurement – no missing decay product extrapolation uncertainties
Also very nice for correlations – hadron vs. other lepton or jet, or even other hadron!
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More fully reconstructed B’sMore fully reconstructed B’s More fully reconstructed B’sMore fully reconstructed B’s
These states are not accessible at B-factories– CP violation in Bs, very small in SM – good place to look
for new physics– Bc coming soon
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bb and B and BS S massesmassesbb and B and BS S massesmasses
M(Bs) = 5365.50 1.29 (stat) 0.94 (sys) MeV/c2
M(B) = 5620.4 1.6 (stat) 1.2 (sys) MeV/c2
World’s best measurements
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Excited B hadronsExcited B hadronsExcited B hadronsExcited B hadrons
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The X(3872) particleThe X(3872) particleThe X(3872) particleThe X(3872) particle
CDF has confirmed BELLE’s discovery of the X particle
• 730 730 90 candidates 90 candidates• ~~12 12 effect effect
MX = 3871.3 0.7 (stat) 0.4 (sys) MeV/c2
220 pb-1
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DØ has also
confirmed the X(3872)
DØ results:
– 300 61 candidates– 4.4effect– M = 0.768 0.004 (stat)
0.004 (sys) GeV/ c2
– Direct (non-B) production
/)3872( JX
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X(3872) production propertiesX(3872) production properties X(3872) production propertiesX(3872) production properties
D0 Run II Preliminary
dl < 0.02 cm 230 ± 59 evts
dl > 0.02 cm 77 ± 25 evts
X mass range decay length (cm)
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X(3872) – X(3872) – (2S) comparison(2S) comparison X(3872) – X(3872) – (2S) comparison(2S) comparison
Is the X charmonium, or an exotic meson molecule? No significant differences between (2S) and X have been
observed yet
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BB++ Lifetimes LifetimesBB++ Lifetimes Lifetimes
2 D mass, decay length fits
CDF: (B+) = 1.66 +/- 0.04 +/- 0.02 psDØ: (B+) = 1.65 +/- 0.08 +/- 0.12* ps
*systematics will be better soon
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BBs s LifetimeLifetimeBBs s LifetimeLifetime
ps (sys) 0.14 (stat) 19.016.0190.1
Bsps (sys) 0.02 (stat) 148.0
129.0330.1 Bs
Bs/0=0.79 0.14 Bs/0=0.89 0.10
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bJ/ Lifetime
B0 J/ K0s bJ/
(b) = 1.25 +/- 0.26 +/- 0.10 ps
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B lifetimesB lifetimes B lifetimesB lifetimes
Same agreement for DØ Tevatron B+,B0 lifetimes are competitive Tevatron b ,Bs are the best
B hadron
CDF measurement (ps)PDG value
(ps)
B+ 1.66 +/- 0.04 +/- 0.021.674 +/-
0.018
B0 1.49 +/- 0.05 +/- 0.031.542 +/-
0.016
b 1.25 +/- 0.26 +/- 0.101.229 +/-
0.080
Bs 1.33 +/- 0.14 +/- 0.021.461 +/-
0.057
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(B+)/(B0) from semileptonic decays (B+)/(B0) from semileptonic decays
Sample compositions:
“D0 sample”: + K+ - + (anything except slow )
B+ 82 % B0 16 % Bs 2 %
“D* sample”: + D0 - + anything
B+ 12 % B0 86 % Bs 2 %
Estimates based on measured branching fractions and isospin
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(B(B++)/)/(B(B00): results): results (B(B++)/)/(B(B00): results): results
(B+)/(B0) = 1.093 0.021 (stat) 0.022 (syst)
Syst. dominated by:
- time dependence of slow reconstruction efficiency - relative reconstruction efficiencies CY
- Br(B+ + D*- + X) - K-factors - decay length resolution differences D0 D*
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Bs MixingBs MixingBs MixingBs Mixing
Measures least known side of unitary triangle
Can not be done at B factories
Difficult measurement – requires:– High yield, good S/B– Oscillations are rapid,
so we need excellent lifetime resolution
– Flavor tagging
World average limit
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Flavor taggingFlavor taggingFlavor taggingFlavor tagging
Opposite jet chargeSame side track charge
Q of the highest pT (or lowest pTrel) track in a cone (dR < 0.7) around the B
Muon charge
Q of the highest pT muon in the event separated in from the signal B by 2.2 rads.
iT
iiT
Σp
.qΣpQJet
Require |Q| > 0.2
b
b d
du
0
B
b
b d
du
0B
u u
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Same side track flavor tagSame side track flavor tagSame side track flavor tagSame side track flavor tag
Same side tags on 1k BJ/K events (update with 4k events coming soon)
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Flavor TaggingFlavor TaggingFlavor TaggingFlavor Tagging
For hadronic final states, DØ triggers on muon from other B – self tagging (=1) with even cleaner dilution due to higher pT threshold: ε D2 ~ 80%
Both experiments plan to use electron tags, and CDF will use kaons
Method DØ
Efficiency
ε (%)
DØ Dilution
D (%)
DØ Tag Power
ε D2 (%)
CDF Tag Power
ε D2 (%)
Jet Charge 46.7±2.7 26.7±6.8 3.3±1.7 In progress
Same side track
79.2±2.1 26.4±4.8 5.5±2.0 2.4±1.2
Muon Tag 5.0±0.7 57.0±19.3 1.6±1.1 0.7±0.1
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BB00 mixing: results mixing: results BB00 mixing: results mixing: results
md = 0.506 0.055 (stat) 0.049 (syst) ps-1
250 pb-1
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Bs mixing -Bs mixing - semileptonic decayssemileptonic decays Bs mixing -Bs mixing - semileptonic decayssemileptonic decays
Easy trigger on lepton in signal – good statistics– DØ: 38 events/pb-1
– CDF: 8 events/pb-1
Degraded proper time resolution due to missing neutrino– DØ: ~ 125 – 150 fs
– CDF: ~ slightly better
Tagging Power– DØ: ε D2 ~ 9 - 12%
– CDF: ε D2 ~ 3 - 8%
If ms ~ 15 ps-1 expect a measurement with 500 pb-1
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Bs mixing -Bs mixing - hadronic decayshadronic decays Bs mixing -Bs mixing - hadronic decayshadronic decays
Difficult trigger, small BR’s – CDF: uses hadronic trigger
0.7 events/pb-1
– DØ: triggers on muon from other B in event: ~ 5 less events, but is starting
to see Bd all hadronic events
Excelent proper time resolution – CDF: = 67 fs
50 fs using inner silicon layer – D0: ~ 90 - 110 fs
will add inner silicon layer in 2005 Tagging Power
– DØ: ε D2 ~ 80 %, self tagging trigger
– CDF: ε D2 ~ 3 – 8 %Need a few fb-1 of data to reach ms > 18 ps-1
DsD*s
and
others
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, , , and direct CPV, and direct CPV, , , and direct CPV, and direct CPV
Resolve the signal composition. Admixture of (at least):
B0d and Charge Conjugate
B0d K+ - and C. C.
B0s KK- and C. C.
B0s K- + and C. C.
pT > 2 GeV/c: TOF doesn’t help
Combine kinematics with dE/dx to achieve statistical separation
Expect ~ 6500 evts / fb-1
MC
Lumi ~ 180 pb-1
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ConclusionsConclusionsConclusionsConclusions
Since the 2003 fall shutdown, the Tevatron has shown substantial improvements
Spring is here, and the Tevatron is blooming with beautiful B results– Some have already been published, many are close
B cross sections, masses, and lifetimes X production studies
Both Experiments are poised to attack Bs mixing in semi-leptonic and hadronic decays.– Bd mixing measured– Expect first Bs results this Fall/Winter
Longer term, many CKM measurements (and other interesting analyses) are in the works.