1

Searching for Searching for New Physics in New Physics in

Beauty and Beauty and Charm Charm

Brendan CaseyBrown University

SMU HEP SeminarJanuary 29, 2007

2

What is new physics?What is new physics?

• Current theories explain the entire dynamics of our universe from about 1 second after birth.

• What was happening before the 1st second?– New physics is what ever it takes to answer this

question.

3

Matter at t Matter at t ≥≥ 1 second: BBN1 second: BBN

Burles, Nollett, Turner astro-ph/99003300

Evolution of light elements in first hour of the universe

But:Small excess of

baryons is an initial condition of BBN, not

a prediction.

No explanation of the evolution of anti-

elements

General Relativity + Astronomy + Particle Physics + Nuclear Physics

4

CPV: Standard Model to the rescue?CPV: Standard Model to the rescue?

mass basis, d,s,b

weak ba

sis, d′, s

′, b′

quarks: d′I = Vij dj

antiquarks: d′i = Vij*dj

Provides a mechanism to generate a net baryon number through decay of heavy to light particles

VVubub ≠≠ VVubub*, *, VVtdtd ≠≠ VVtdtd** ⇒⇒ CPVCPV

productiondeca

y

5

Standard Model CPVStandard Model CPV

Mag(CPV) ≈ f(m2j-m2i) × f(θij) × sinφCP

Three properties govern size of CPV in SM:

• quarks:– Large mass splitting ↑– Small mixing angles ↓– Large φCP ↑

• neutrinos:– small mass splitting ↓– large mixing angles ↑– φCP ?

~15 orders of magnitude too small

Huet, Sather PRD51 379 (1995)Jury still out

Need new sources of CPV!More generations, more interactions….new particles

6

Direct versus IndirectDirect versus Indirect

0.1

1

10

100

1000

1965

1970

1975

1980

1985

1990

1995

2000

Year

quar

k m

ass

(GeV

/c2 )

t

t

1 TeV p

1 TeV p

5 GeV B 5 GeV Bt

t

b d

b d

WW

charm discovered

1974

bottom discovered

1977

top discovered

1995

directindirect

7

Direct versus IndirectDirect versus Indirect

0.1

1

10

100

1000

1965

1970

1975

1980

1985

1990

1995

2000

Year

quar

k m

ass

(GeV

/c2 )

t

t

1 TeV p

1 TeV p

5 GeV B 5 GeV Bt

t

b d

b d

WW

charm discovered

1974

bottom discovered

1977

top discovered

1995

charm predicted, mass scale set by

K→µµ1970

bottom and top predicted from CPV in kaon mixing

1973

Top mass scale set from Bd mixing

1987

directindirect

8

Cast of CharactersCast of CharactersMesons

B0: ( b d ), Bs: ( b s ), D+: ( c d ), Ds: ( c s )

Neutral Flavor Changing Interactions

b t s

b t s

Box:

Penguin:

Rate ≈ ( mt / mW )2

9

ApparatusApparatus

10

The The TevatronTevatron and Dand DØØ DetectorDetector

MAIN INJECTOR (MI)

LINAC

BOOSTER

120 GeV p

8 GeVINJ

p ABORT

TEVATRON

p ABORT

SWITCHYARD

RF150 GeV p INJ150 GeV p INJ

p SOURCE:DEBUNCHER (8 GeV) &ACCUMULATOR (8 GeV)

_

p_

pF0

A0

CDF DETECTOR& LOW BETA

E0 C0

DO DETECTOR& LOW BETA

p (1 TeV)

p (1 TeV)_

TeV EXTRACTIONCOLLIDER ABORTS

_

B0

D0

_

P1

A1

P8

P3

P2

TEVATRON EXTRACTIONfor FIXED TARGET EXPERIMENTS

& RECYCLER

PRE-ACC

NS

W

E

(150 GeV)

(8 GeV)

(8 GeV)

(400 MeV)

400 MeV

150 GeV

~1 TeV + 1 TeV

11

~700 Scientists

83 institutions

20 countries

4 continents

(big parties, good food, exotic

meeting locations…)

~70 Member B group with ~20 people working on mixing and CPV ~2 working on charm

Comparison: ~100-300 member groups working on mixing and CPV in the Belle, BaBar, CDF, and LHCb collaborations.

12

Why the Why the TevatronTevatron??

Don’t they do B physics at B factories now?

~1-2~0.5Longitudinal boost

~1-2~0Transverse boost

~100 Hz0Bs production rate

~1 kHz~10 HzB production rate

Tevatron@ L = 1032 cm-2s-1

B factory on ϒ(4S) @ L = 1034 cm-2s-1

Tevatron is the only Bs factory

13

Why Why DDØØ??

Excellent muon identification

Large semileptonic B samples ideal for mixing and CPV studies

Uranium

Iron

14

Why Why DDØØ??

Excellent vertexingcapabilities for flight length

determination

Just enough resolution to probe SM expected value of

the Bs mixing frequency

Error on the flight length determination

15

TevatronTevatron Data SetData Set>2.2 fb-1delivered

FY01 FY02 FY03 FY04 FY05 FY06 FY07

Run IIa: 1.3 fb-1 on tape Run IIb: 700 pb-1 analyzed

16

TevatronTevatron Data SetData Set>2.2 fb-1delivered

FY01 FY02 FY03 FY04 FY05 FY06 FY07

Run IIa: 1.3 fb-1 on tape Run IIb: 700 pb-1 analyzed

Fast turn around in the heavy flavor group

10 1.0 fb-1 results last winter

Pushing for close to 2 fb-1 results this winter

17

BBss MixingMixing

18

Neutral Meson MixingNeutral Meson Mixing

( )

( )outincube

outincube

−=

+=

212,

211,Is the cube going into

the page or coming out of the page?

Time Evolution of a two state neutral meson system:

( )( )

( )

∆±

∆Γ=

+=

+=

Γ−±

+−

−+

mttetg

MtgMtgtM

MtgMtgtM

t

cos2

cosh2

)(

)()()(

)()()(

2

2

1 Matter and antimatter constantly talk to each

other!

∆Γ: width(lifetime) difference, ∆m: mass difference between states

19

• General rule of neutral flavor changing processes:– New physics:

• Second order loop or box• New particles can enter the loop• SM contribution is suppressed

– Precision SM tests:• no new physics? Measure fundamental Standard Model

parameters• clean in B mesons

– b quark is heavy,– top loop dominates.

• Every measurement of mixing has lead to a major discovery:

• K: CPV, 3rd generation, Bd: top mass, ν: neutrino mass

Why Mixing?Why Mixing?

b???

s

b tVtd(s)

s,d

Rate ≈ ( mt / mW )2s,d

20

Analysis OverviewAnalysis Overviewµ+ νµ

π −

K+K−

µ+,e+

Σ qBs Candidate

Recoil system

Primary and secondary vertices

Reconstruct the Bs in a flavor specific final state

Determine lifetime in the Bs rest frame

Determine initial flavor by studying recoil system Extract the mixing frequency from the time dependence of mixed and

unmixed samples

)cos1()( / tmet st ∆±≈Γ − τ

Bs⇒ Bs ⇒ Bs ⇒ Bs

21

Mixing Frequency ExtractionMixing Frequency Extraction

Reconstructed decay length (cm)

22

Mixing Frequency ExtractionMixing Frequency Extraction

Reconstructed decay length (cm)

Looking for this

Reconstructed decay length (cm)

23

Mixing Frequency ExtractionMixing Frequency Extraction

Reconstructed decay length (cm)

Perform a Fourier analysis of the decay length distribution to extract

the mixing frequency

Power Spectrum for winter data set

Time domain

Frequency domain

1/∆m

∆m

24

Winter 06 Mixing Frequency ResultsWinter 06 Mixing Frequency Results

17 < ∆ms < 21 ps-1 @ 90% CLMaximum likelihood at ∆ms = 19 ps-1

1 fb-1

First time ∆ms bounded on both sides!!!!!

Change in –log(L) versus ∆ms

Ds→φπ only

25

ReflectionsReflections

m(Κ∗Κ) m(ΚSΚ)

Ds→K*K D+→Kππ Λc→pKπ Ds→KSK D+→KSπ Λc→KSp

Original results based on Ds→φπ

Needed to add more channels: K*K and KSK

Difficult to include these modes without particle identification

26

Taming ReflectionsTaming Reflections

Momentum asymmetry between KS and K candidate

Take advantage of the fact that the mass shift is a function of the track momentum

D+→KSπMC

m(Κ

SΚ)

m(Κ*Κ)

m(Κ*Κ)

High p

low p

27

Fall 06 ResultsFall 06 Results

φπ µφπ µ

K*K µ φπ e

ΚSΚ µ

Extra data ‘cured’ fluctuation

28

Time Evolution of ResultsTime Evolution of Results

02468

1012141618202224262830

19921994

19961998

20002002

20042006

2008

LEP/SLD/CDF I were able to exclude values below about 15 ps-1

New Physics Realm

∆ms LEP/SLD Era

SM expectation

29

Time Evolution of ResultsTime Evolution of Results

02468

1012141618202224262830

19921994

19961998

20002002

20042006

2008

March 06: DØ provides first upper bound on the Bs oscillation frequency. Rules out large new physics effects at high confidence

level. Still 5% chance of background fluctuation.

∆ms

New Physics Realm

SM expectation

DØ, March 2006

30

Time Evolution of ResultsTime Evolution of Results

02468

1012141618202224262830

19921994

19961998

20002002

20042006

2008

Confirmed by CDF in April 2006. >5σ measurement Fall 2006.Closes the chapter on the magnitude of the Bs oscillation frequency.

∆ms

New Physics Realm

SM expectation

Tevatron Era

17.7+/- 0.12 ps-1

31

Indirect Searches so farIndirect Searches so far

• Now reached SM level for one of our key indirect NP search modes, ∆ms.– No new physics.

• Not just a Tevatron problem, problem for B physics in general.

• Choice:– Wait for new energy frontier– Expand current physics program

• beauty → charm

32

Flavor Changing Neural Flavor Changing Neural Current Charm DecayCurrent Charm Decay

33

Up versus DownUp versus Down

1

10

100

1,000

10,000

100,000

1,000,000

0 1 2 3 4Generation

Mas

s (M

eV/c

2 )

up lineq = 2/3

down lineq = −1/3

t

c

ud

s

b

34

Up versus DownUp versus Down

1

10

100

1,000

10,000

100,000

1,000,000

0 1 2 3 4Generation

Mas

s (M

eV/c

2 )

up lineq = 2/3

down lineq = −1/3

t

c

ud

s

b

Very different mass hierarchy

35

Up versus DownUp versus Down

1

10

100

1,000

10,000

100,000

1,000,000

0 1 2 3 4Generation

Mas

s (M

eV/c

2 )

t

c

ud

s

b

c ub

W+ W−

up FCNC~ ( mb / mW )2

W− W+b st

down FCNC~ ( mt / mW )2

36

Up versus DownUp versus Down

1

10

100

1,000

10,000

100,000

1,000,000

0 1 2 3 4Generation

Mas

s (M

eV/c

2 )

t

c

ud

s

b

c ub

W+ W−

up FCNC~ ( mb / mW )2

W− W+b st

down FCNC~ ( mt / mW )2

Down the down line: suppressed but measurable (eg. mixing)Down the up line: almost impossible for SM ⇒

unambiguous signal of NP

37

Why 3 body FCNC charm?Why 3 body FCNC charm?

D+ → π µ+ µ−m( µ+ µ−)

(GeV)

0.5 1.0 1.5

(1/Γ

)(dΓ

/dm

2 )(G

eV-2

) 10-4

10-6

10-8

10-10

Long distance

Short distance

c u

µ

µ

Interested in short distance (weak scale) but also need to worry about long

distance (QCD scale)

Clear separation of long distance and short distance componentsNew Physics only effects short distance. (rare clean channel)

µ

µc s

su

dD+

π+

φ D→φπ

D→πµµ

38

New Phenomena in New Phenomena in cc →→ u u µµ+ + µµ−−

Strict limits from b→ s, interesting scenarios effect up sector quarks and not down sector quarks.

39

New Phenomena in New Phenomena in cc →→ u u µµ+ + µµ−−

Strict limits from b→ s, interesting scenarios effect up sector quarks and not down sector quarks.

D+ → π µ+ µ−

m( µ+ µ−) (GeV)0.5 1.0 1.5

(1/Γ

)(dΓ

/dm

2 )(G

eV-2

)

10-4

10-6

10-8

10-10

RPV in the up sector and not the down sectorBurdman et al. hep-ph/0112235

c → u µ+ µ−

40

New Phenomena in New Phenomena in cc →→ u u µµ+ + µµ−−

Strict limits from b→ s, interesting scenarios effect up sector quarks and not down sector quarks.

D+ → π µ+ µ−

m( µ+ µ−) (GeV)0.5 1.0 1.5

(1/Γ

)(dΓ

/dm

2 )(G

eV-2

)

10-4

10-6

10-8

10-10

RPV in the up sector and not the down sectorBurdman et al. hep-ph/0112235

c → u µ+ µ−

Little Higgs models with new up sector vector quark

Fajfer et al. hep-ph/0511048factors of >1000 over SM not ruled out.

41

m(µ+µ−) (GeV/c2)E

vent

s / 5

MeV

/c2

D D SelectionSelectionRequire well reconstructed track

in the muon spectrometer matched to a central track with

pT>2 GeV , p > 3 GeV

First select φ → µ+ µ−0.96 < m(µµ) < 1.06 GeV

φ

1.3 fb-1

track multiplicity

trks per µ+µ− event

trks per µ+µ− jet

Combine µ+ µ− with a track in the same jet and select D candidate

1.4 < m(πµµ) < 2.4 GeV

ω

ρη

42

M0 5 10 15 20 25 30 35 40 45 50

0

20

40

60

80

100

120

140

160

180

200

Best Track SelectionBest Track SelectionLarge track multiplicity leads to several candidates per event.

Select best track based on the D vertex χ2, and distance between the track and the dimuon system

M = χ2 + ∆R2

All candidates

false candidates

correctcandidate

Candidate

multiplicity

0 5 10 15 20 25

φπ MC

43

ΘDSD

ID

Sπ

x

p

π

µ

µ

Background SuppressionBackground Suppression

Isolation

Flight length significance

π impact parameter

significance

Colinearityangle

pion impact parameter significance (Signal MC)0 5 10 15 20 25

0

20

40

60

80

100

pion impact parameter significance (D+ MC)0 5 10 15 20 25

0

10

20

30

40

50

60

70

80

90

pion impact parameter significance (sideband data)0 5 10 15 20 25

0

20

40

60

80

100

120

140

160

180

200

220

240310×

Sπ

Ds MC

D+ MC

data sidebands

44

Results for Resonance ProductionResults for Resonance Production

m(µ+µ−) (GeV/c2)

Eve

nts

/ 5 M

eV/c

2

D→φπ+→π+µ+µ− D∅

m(π+µ+µ−) (GeV/c2)

Eve

nts

/ 50

MeV

/c2

Long Distance D → φ πDimuon invariant mass

n(D+) = 115 +/- 33> 4 sigma

n(Ds) = 254 +/- 38

BF( D+ → φ π → π+ µ+µ−) = (1.41 +/- 0.40 +/- 0.46) x 10-6

(PRL for 1.3 fb-1 result about to be released.)

D significance > 5Pion IP significance > 0.5

1.3 fb-1

45

Long Distance to Short DistanceLong Distance to Short Distance

D→φπ+→π+µ+µ− D∅

m(π+µ+µ−) (GeV/c2)

Eve

nts

/ 50

MeV

/c2

Long Distance D → φ π

n(D+) = 115 +/- 33> 4 sigma

n(Ds) = 254 +/- 38 Long distance:φ mass cut removes most background

Short distance:Now need to make an anti φ cutNow have ~150k background events to remove

1.3 fb-1

46

More Background ReductionMore Background ReductionNext step: continuum production. Much larger dimuon

phase space requires more stringent requirements

47

Continuum ResultsContinuum ResultsD→π+µ+µ− D∅

m(π+µ+µ−) (GeV/c2)

Eve

nts

/ 50

MeV

/c2

n = 19n(bkg) = 31 +/- 4

Short Distance D →πµµ

(PRL for 1.3 fb-1 result about to be released.)

1.3 fb-1

BF( D → πµµ )

48

Continuum ResultsContinuum ResultsD→π+µ+µ− D∅

m(π+µ+µ−) (GeV/c2)

Eve

nts

/ 50

MeV

/c2

n = 19n(bkg) = 31 +/- 4

Short Distance D →πµµ

How are we doing?factor of ~4 better than dedicated charm experiments

Factor of ~10 better than Bfactories

1.3 fb-1

BF( D → πµµ )

49

ConclusionsConclusions

50

ConclusionsConclusions• DØ Heavy Flavor program producing several world’s first or

world’s best results – 4 years ago prevailing opinion was that you don’t do B physics at DØ

• Presented today:– First upper limit on the Bs mixing frequency

• no smoking gun for new physics in ∆ms– Best limits on new physics in rare charm decays.

• Basically rules out possibility of finding a smoking gun in charm.

• Results:– Demonstrated a lack of enhancement in almost all low energy FCNC

processes.• Tells you that the next theory beyond the standard model must have

mechanisms that supress FCNC

• Next steps:– Go find these new particles directly at the LHC