jet results

CERN: August 2002 F. Bedeschi, INFN-Pisa

Jet Results

HADRONIC JETS


Hadronic jets High Et jet at D0 in Run 1

Et1 = 475 GeV Et2 = 472 GeV 1 = -0.69 2 = 0.69

Side view


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


Inclusive jets

Jet Et cross sections match quite well SM predictions over several orders of magnitude

CDF

D0


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


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


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


Jets and pdf’s

Tevatron extends coverage to high values of x, Q

Tevatron

HERA

Fixed target


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


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


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


b-quarks

b-quark production and decay


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))


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


A real B event


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


b-quark samples

Exclusive B decays with J/ and kaons

B+ K+

B0 K0*


b-quark production

b-quark production:Leading order ~ next-to-leading order

LO

NLO


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


b-quark production

Recent developments (Cacciari et al.) suggest that this can be improved with better fragmentation

CDF data

B+ meson cross section


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


B-hadron decays

Lifetime summary and example

Bu B+


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


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


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


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


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)


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


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


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


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)


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


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 =



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



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)



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


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)



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



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


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


b-decay: CP violation (prospects)

Tevatron experiments can become competitive with B factories within a few years on this measurement

May 2002


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.


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

jet results

Documents

d0 p d0

d0 data

signal of quark compositeness

sm predictions

argvubbquark productionhow

jet physicsrun

test sm production

pdfs tevatron