jet results
DESCRIPTION
Jet Results. HADRONIC JETS. Hadronic jets. High Et jet at D0 in Run 1 E t1 = 475 GeV E t2 = 472 GeV h 1 = -0.69 h 2 = 0.69 Side view. Hadronic jets. EM calorimeter energy. Hadronic calorimeter energy. High Et jet at CDF in Run II E t1 = 403 GeV, E t2 = 322 GeV - PowerPoint PPT PresentationTRANSCRIPT
CERN: August 2002 F. Bedeschi, INFN-Pisa
Jet Results
HADRONIC JETS
CERN: August 2002 F. Bedeschi, INFN-Pisa
Hadronic jets High Et jet at D0 in Run 1
Et1 = 475 GeV Et2 = 472 GeV 1 = -0.69 2 = 0.69
Side view
CERN: August 2002 F. Bedeschi, INFN-Pisa
Hadronic jets High Et jet at CDF in Run II
Et1 = 403 GeV, Et2 = 322 GeV 1 = 0.037, 2 = -0.364
“Lego plot”: vs. Rview
EM calorimeter energy
Hadronic calorimeter energy
Each cell is a calorimetric tower
CERN: August 2002 F. Bedeschi, INFN-Pisa
Inclusive jets
Jet Et cross sections match quite well SM predictions over several orders of magnitude
CDF
D0
CERN: August 2002 F. Bedeschi, INFN-Pisa
Inclusive jets
After a detailed comparison with theory… however
CDF observed an excess in the high end of the spectrumSuch an excess could be a signal
of quark compositeness!D0 did not see a clear effect
CERN: August 2002 F. Bedeschi, INFN-Pisa
Inclusive jets
After years of work and discussions:Effect is related to pdf choice (newer pdf’s do better)CDF and D0 agree
CDF data
CERN: August 2002 F. Bedeschi, INFN-Pisa
Inclusive jets
Conclusion is that one has to boost gluon content at high x to match CDF and D0 data with theory. Can be done without conflicts with previous data of other experiments Happens naturally with latest sets of pdf’s including Tevatron jet data
CERN: August 2002 F. Bedeschi, INFN-Pisa
Jets and pdf’s
Tevatron extends coverage to high values of x, Q
Tevatron
HERA
Fixed target
CERN: August 2002 F. Bedeschi, INFN-Pisa
Jet angular distribution
Jet angular distributions are less sensitive to details of pdf’s Best compositeness limits set with this method No effect observed
= (1+cos *)/(1-cos *) = polar angle in jet system center of mass
CERN: August 2002 F. Bedeschi, INFN-Pisa
Future of jet physics
Run 1 – 87/pb Run IIA – 2/fb Run IIB – 15/fb
Can probe much higher jet energies
Look for new excesses in the high end of the spectrum
Run 1
Run IIA Run IIB
Run IIB
Run IIA
CERN: August 2002 F. Bedeschi, INFN-Pisa
Jet Summary
What did we learn? Jets are an experimental signature of quarks and gluons Jet production tests the SM predictions for quark and gluon
interaction dynamics Jet production at the Tevatron is sensitive to pdf’s in a region
not fully covered by other experimentsDeviations from SM predictions that cannot be absorbed in
the pdf’s can signal new physics. In particular quark compositness
SM model will be tested at an even deeper level with data collected during the ongoing Run II of the Tevatron
CERN: August 2002 F. Bedeschi, INFN-Pisa
b-quarks
b-quark production and decay
CERN: August 2002 F. Bedeschi, INFN-Pisa
b-quarks
b-quarks are the second heaviest quarks observedMb ~ 5 GeV/c2 can still be copiously produced at Tevatron
b ~ 100 mb (cfr. b ~ 1 nb at B-factories, ~ 5 nb at LEP)
S/N ~ 10-3 (cfr. 0.2 at B-factories, 0.14 at LEP)
Interest of b-quarks:Production: test SM production in region with a different
characteristic mass scaleMass protects calculations from infrared and collinear divergences
Decay: ideal for measuring elements of CKM matrix which couple to third generation quarks
Mixing (|Vtd|, |Vts|)
CP violation (arg(Vtd), arg(Vub))
CERN: August 2002 F. Bedeschi, INFN-Pisa
b-quark production
How do I tell I made a b-quark? Charm mesons, D, in decay products Leptons from SL decay:
~10% for each mode
Large mass large ptrel
Leptons from J/ decay:B J/ + X 1%J/e+ e- 6% each
Secondary vertex:c ~ 450 m<Nch> ~ 5
B
b
q c
W-
l -
qD
B
b
q
c
W-c
sq
J/
K
CERN: August 2002 F. Bedeschi, INFN-Pisa
A real B event
CERN: August 2002 F. Bedeschi, INFN-Pisa
b-quark samples
Charm signals in events with leptons Sign of lepton correlated with that of kaon
Shaded area corresponds to wrong sign combinations
D0 K-+
D*+ D0 +
D0 K-+
D*+ D0 +
D0 K- 3
D*+ D0 +
D0 K-+ 0
CERN: August 2002 F. Bedeschi, INFN-Pisa
b-quark samples
Exclusive B decays with J/ and kaons
B+ K+
B0 K0*
CERN: August 2002 F. Bedeschi, INFN-Pisa
b-quark production
b-quark production:Leading order ~ next-to-leading order
LO
NLO
CERN: August 2002 F. Bedeschi, INFN-Pisa
b-quark production
Observed x-sections are higher than SM predictions by ~factor 2.5 – 3 Much work to understand this
Good consistency observed between CDF and D0 results
b-quark cross section
CERN: August 2002 F. Bedeschi, INFN-Pisa
b-quark production
Recent developments (Cacciari et al.) suggest that this can be improved with better fragmentation
CDF data
B+ meson cross section
CERN: August 2002 F. Bedeschi, INFN-Pisa
B hadron decays
B hadron decays dominated by b-quark decayEffect of spectator quarks can be included with
perturbative expansions in terms of 1/mb Expect small differences between lifetimes of different species
Measurement of lifetimes test accuracy of these methods and the SM
B
b
q c
W-
q1
q2
qD
CERN: August 2002 F. Bedeschi, INFN-Pisa
B-hadron decays
Lifetime summary and example
Bu B+
CERN: August 2002 F. Bedeschi, INFN-Pisa
b-quark decays: CKM matrix
CKM matrix describes flavor mixing in charged weak current transitionsAll up-type quarks (u, c, t) can couple with any down-
type quarks with a strength modulated by the elements of the CKM matrix
b
u
W
Vub
Vud
Vcd
Vtd
Vus
Vcs
Vts
Vub
Vcb
Vtb
Vtd = |Vtd |ei
Vub = |Vub |ei
CKM matrix =
CKM matrix must be unitary if there are only 3 generations
Only 2 elements are complex
CERN: August 2002 F. Bedeschi, INFN-Pisa
b-quark decays: CKM matrix
If CKM unitary can be expressed in powers of Vus = = sin(Cabibbo) ~ 0.22Wolfenstein representation
12
1
21
23
2
2
3
2
)1(
)(
AiA
A
iA
Measurement of CKM elements allows test of unitarity triangle is closed1st, 3rd col.: VudVub*+VcdVcb*+VtdVtb*=0Other triangles less interestingLet: Vud = 1, Vcd = -Vtb = 1
Vub*+ Vtd = Vcb* O (3%)
Divide by A3 = Vcb* = - Vts
(+i)
Vub*
Vcb
(1--i)
Vtd
Vts
Mixing
Angles: CP violation
Cha
rmle
ss
CERN: August 2002 F. Bedeschi, INFN-Pisa
b-decays: CKM matrix
Vub/ Vcb is related to fraction of b-hadron decays with no charm in final state Hard to measure at hadron colliders. Done at CLEO, LEP, B-factories
Vtd/ Vts is related to an effect called mixing (see later) Hadron colliders are very competitive and are the only place where Vts can be
measured directly
The angles of the triangle are related to CP violation effects (see later) Hadron colliders and B-factories complement each other in these difficult
measurements
CERN: August 2002 F. Bedeschi, INFN-Pisa
b-decays: mixing
Some probability that a B0 turns into a B0 due to higher order box diagrams
m mt2 |Vtd,s|2
x = m
Bd,s
W
b
d, s
uct
W
b
d, suct
Bd,s
Bd,s W
b
d, sW
b
d, su c t
Bd,s
u c t
txemtetBBBBP
ttcos1
2)]cos(1[
2|)(|)(
//20000
CERN: August 2002 F. Bedeschi, INFN-Pisa
b-decays: mixingTypically what is measured is the mixing
asymmetry evolution with proper decay time:A = = cos(m t) (t = proper time lived)
How do we know if B0 has mixed or not?Type of B0 at time of decay defined by final state
E.g. B0 D l+ : sign of lepton tags the B typeType of B0 at production is much harder!
Use several methods of “flavor tagging” (see later)Such methods are not perfect:
w = probability to mistagD = dilution = 1-2wFinite efficiency =
Observed asymmetry: Aobs(t) = D A(t) = D cos(m t)Amplitude measures dilutionFrequency measures mixing
Nnomix(t) - Nmix(t)Nnomix(t) + Nmix(t)
CERN: August 2002 F. Bedeschi, INFN-Pisa
Flavor tagging
Opposite side techniques: b-quarks are produced in pairs by
the strong force that conserves flavor: always one b and one anti-b
Determine the type of the second b in the event at the decay
Mixing of the second b contributes to the dilution
Use signatures like sign of lepton, kaon (from charm decay), jet charge (estimator of leading quark charge)
Same side techniques: Sign of nearby has sign
correlated to b type
Same side
Signal side
Opposite side B
Jet Qtag
Lepton/K Q tag
CERN: August 2002 F. Bedeschi, INFN-Pisa
b-quark decay: mixing
Only B0 mix! Do not want to violate charge conservation2 possibilities: B0
d, B0s
|Vtd|2 ~ 2|Vts|2 ~ 0.05 |Vts|2 md << ms
B0d mixing measured extensively
B0d easier to produce
Mixing frequency slow no special resolution needs
No observation of B0s mixing so far
Smaller cross sectionHigh mixing frequency need very good vertex resolution
CERN: August 2002 F. Bedeschi, INFN-Pisa
b-quark decay: Bd mixing
Example:CDF measurement of mixing
Signal: B0d D(*) + X
Sign of D flavor at decay
Flavor tag: opposite side leptonSign of lepton flavor at production
CERN: August 2002 F. Bedeschi, INFN-Pisa
b-decay: Bd mixing
Summary of Tevatron Run 1 B0d mixing
results and comparison with LEP Current world average dominated by
Belle/BaBar: md = 0.496 ± 0.007(ICHEP 1998)
(1998)
CERN: August 2002 F. Bedeschi, INFN-Pisa
b-decay: Bs mixing
Extracting the CKM matrix elements from m has many theory uncertainties:
fBd and BBd are both known to ~ 15% from lattice calculations
Ratio = fBs BBs/fBd BBd ~ 1.160.05
The ratio |Vts|/ |Vtd| can be measured with much less theory uncertainty (~ 4-5%)
Much expectation for ms measurement at Tevatron
CERN: August 2002 F. Bedeschi, INFN-Pisa
b-decay: Bs mixing (prospects)
Measure mixing asymmetryAmix (t) =
Fit to a(t) = D cos(xs t/)
Nnomix(t)-Nmix(t)
Nnomix(t)+Nmix(t)
Significance of measurement related to depth of likelihood minimum relative to x =
CERN: August 2002 F. Bedeschi, INFN-Pisa
b-decay: Bs mixing (prospects)
Signal (N): Need all charged hadronic mode for resolution and statistics secondary vertex trigger is essential
Bs Ds , Ds 3
D+s K0* K, K0
S K
Expectations for Run IIA in 2 fb-1:20,000 events (P-909)75,000 Yellow Book
S/B: ~ 1:1 from Run I extrapolations
Assume 1:2 – 2:1 rangeSmall effect on significance
BN
Nts
x
eDN
LsxSignif
2
2)/(
2
2)ln(2)(
CDF preliminary
Run II data Few pb-1
CERN: August 2002 F. Bedeschi, INFN-Pisa
b-decay: Bs mixing (prospects)
Flavor tagging D2:Expect 5.7 % from Run I (6.3% measured in sin(2) analysis)
+3.2% (SS Kaon) + 2.4% (OS Kaon) = 11.3% total
Proper Time Resolution:Assume 45 fsec (perfect L00) to 70 fsec (L00 doesn’t work)
CERN: August 2002 F. Bedeschi, INFN-Pisa
b-decay: Bs mixing (prospects)
5 xs significance as a function of the available luminosity Xs mixing parameter should be within reach rather soon
The two curves refer to two extreme values of the c resolution: L00 proposalL00 not usable
Red line is the SM central value Orange line are current 95% CL limits from combined analyses (hep-ph/0112133)
With 2 fb-1 expect reach ~ 60 with conservative assumptions
0
10
20
30
40
50
60
70
80
0 100 200 300 400 500
5 xs reachYellow Book 2000
Luminosity
0
10
20
30
40
50
60
70
0 100 200 300 400 500
5 xs reachBTB PAC proposal
Luminosity
CERN: August 2002 F. Bedeschi, INFN-Pisa
b-decay: CP violation
CPviolation: (Bf) (Bf) Special simplest case f is CP eigenstate
e.g. f = J/ K0S
Bd
W
b
d
uct
W
b
d, suct Bd
Direct and mixed path interfere
A(BdBd) mt2 Vtd
2 ~ |A|ei2
A(BdBd) mt2 V*td
2 ~ |A|e-i2
B0 f
B0mix ei2
B0 f
B0mix e-i2
Asymmetry measures sin(2)
ACP= = sin(2) sin(mdt)
(B0 f) (B0 f) (B0 f) + (B0 f)
CERN: August 2002 F. Bedeschi, INFN-Pisa
b-decay: CP violation
As usual one measures: Aobs(t) = D ACP(t) = D sin(2) sin(mdt) Important to calibrate dilution with mixing analyses
Typical CP eigenstates have small Branching Ratio’s ~ 10-5! Large b x-section at Tevatron is very useful
CDF Run 1 measurement is not competitive with B-factories, but it is very useful to estimate our future capabilities in Run II
OPAL
CDF
ALEPH
BaBar
Belle
World Average March 2002
SM indirect limits
-0.50 0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00
Measurements of sin(2) as of March 2002
CERN: August 2002 F. Bedeschi, INFN-Pisa
b-decay: CP violation
CDF Run 1 result is based on: ~ 400 B0 J/ K0
S
All available taggers:Opposite side: lepton, Jet-chargeSame side: pion charge correlation
Result:
~ 400
B K0S
sin(2) = 0.91 + 0.37- 0.36
Asymmetry
Vs. lifetime
CERN: August 2002 F. Bedeschi, INFN-Pisa
b-decay: CP violation (prospects)
Extrapolation based on analytic formula for the error on the time integrated asymmetry:
In addition we account for improvements made by studying the time evolution
Expectations in 2 fb-1:
N
B N
N D
1
x
x 1 ) ) (2 sin (
2d
2d
Time integrated Time dependent
Scenario D2 N(Ks) (sin2 ) (sin2 ) Run I 6.3% 400 0.57 0.46Run II, No tag improvements 6.3% 20,000 0.08 0.07Run II, with Kaon tagging 9.1% 20,000 0.07 0.05
CERN: August 2002 F. Bedeschi, INFN-Pisa
b-decay: CP violation (prospects)
Tevatron experiments can become competitive with B factories within a few years on this measurement
May 2002
CERN: August 2002 F. Bedeschi, INFN-Pisa
CKM matrix current status
Compatibility between various measurements indicates consistency with SM predictions
(May 2002)
This test will be much stronger after Bs mixing will be measured and more accurate measurements of sin(2) will be available.
CERN: August 2002 F. Bedeschi, INFN-Pisa
b-quark Summary
What did we learn?b-quarks are heavy, but not to heavy to prevent copious
production rates:Excellent window over third generation
b-quark production has been puzzling for some time, but more accurate use of NNLO calculations and fragmentation functions partially reduces the problem
Some fundamental parameters of the SM model, in particular the modulus and the phase of the elements of the CKM matrix coupling to the third generation can be measured studying B mesons
Measurements of mixing and CP violation at the Tevatron will contribute significantly to a better understanding of this part of the SM