clara matteuzzi qcd 2007 martina franca 1 clara matteuzzi qcdworkshop martina franca, june 16–19,...

Clara Matteuzzi QCD 2007 Martina Franca 1

Clara Matteuzzi

QCDWorkshopMartina Franca, June 16–19, 2007

B physics in the LHC program

Does flavor physics in the LHC era increase our understanding?

INFN and Universita Milano-Bicocca


Contents

1. Present status of the CKM

2. The start up of LHC 3. Experiments at LHC: potential (some examples)4. B physics beyond 2009


• The PEP-II/BABAR and KEKB/Belle B Factories, together with CLEO-c and recent K decay experiments, have reached the precision measurement regime for many parameters

• CDF and DØ at Tevatron Run II are now producing

beautiful results on Bs mixing, rare decays and b baryon studies

Where is Flavour Physics now ??


Accuracy of angles is limited by experiment:α ~ ± 12°β ~ ± 1°γ ~ ± (20°-30°) χ not yet measured

= 0.2258±0.0011 A = 0.83±0.02

= 0.168±0.029 = 0.340±0.017

Current status of CKM parameters

With 2 ab-1 δ(ρ,η) = (10%,4.4%)

Accuracy of sides is limited by theoretical uncertainty


All measurements related with electroweak quark transitions are coherent with the CKM picture of the Standard Model

Overconstrained tests of the CKM matrix to the level of precision warrented by theoretical uncertainties (will theory be able to calculate hadronic parameters with 1% precision in 10 years?)

The CKM phase is consistent with being the source for all observed CP-violating phenomena

There must, however, be additional sources of CP violation

Goal of heavy flavour physics is now shifting fromunderstanding of CKM in the Standard Model (SM)

tosearch for physics Beyond the Standard Model (BSM)appearing in loops.

Current status of CKM parameters


ATLAS/LHCf

LHCb

ALICE

CMS/TOTEM

The LHC era begins ……..


LHC starts at √s = 14 TeV middle of 2008

ALICE heavy ion and pp experimentATLAS general purpose pp experimentCMS general purpose pp experiment LHCb dedicated Heavy Flavour experiment

Middle of 2008: Start of run @ s = 14 TeVcalibration and trigger commissioning, increasing luminosity toward 1033 for ATLAS/CMSand ~21032 for LHCb for physics

From 2009: Stable physics run @ s = 14 TeVATLAS and CMS: clear interest to increase luminosities towards 1034 as quick as possible. B physics will become increasingly difficult.LHCb: collecting data with <1033 for some years

The LHC experiments


2008physics run for a period of 1/4 of the nominal year (107 sec)<L>=1033 for ATLAS and CMS (optimistic?)<L>=21032 for LHCb (should be possible…)

Ldt = 2.5 fb each for ATLAS and CMS(if <L> is lower, trigger could be adjusted to have a similar number of b’s)

Ldt = 0.5 fb for LHCb2009-2011 ATLAS and CMS accumulate Ldt = 30 fb eachend of B physics era and move to 1034 regime (except Bs)

2009-2013

The stage ………..

LHCb collect Ldt ≥ 10 fb data by the end of 2013±1

The flavour stage


• BABAR and Belle will each have collected a total data sample of approximately 1 ab-1 by ~2008– 2 ab-1 = 2 x 109 produced B0B0, B+B- pairs

• The Tevatron Run II experiments CDF and DØ will each have collected ≤ 8 fb-1 by ~2009

CDF and D0, well understood detectors

Data samples at the start of the LHC era

The flavour stage


Given the fact that– LHC will be the facility producing the largest number of b

hadrons (of all types), by far, and for a long time – the Tevatron experiments have demonstrated the feasibility

of B physics at hadron machinesPerform a dedicated b-physics experiment at the LHC– to exploit the huge bb production

in the not-well-known forward region, despite the unfriendly hadronic environment (multiplicity, …) for b-physics

• ~ 230 b of bb production in one of the forward peaks (400 mrad),corresponding to nearly 105 b hadrons per secondat a low luminosity of 21032 cm–2s–1

b - physics at the LHC


The LHCb spectrometer

VertexLocator(Silicon)

RICH counters/K/p Identification

Tracking CalorimetersMuonSystem

Dedicated to b physicsWorks at L=2x1032 cm-2 sec-1

1.9 < < 4.9 or15 < < 300 mrad

Special features: a dedicated trigger and Particle Identification


The LHC experimentsCentral detectors | η | < 2.5

b physics trigger:

high pt leptons (6-7 GeV/c , 12 GeV e)

no hadronic trigger Mostly b physics with J and rare decays with leptons (and at low luminosity)

CMS ATLAS


Particles Identification in

LHCb • Efficient hadron PID crucial for many channels.• Calibration of K/ PID on data will be performed using the D*+D0+, D0 K+- decay chain

Ex. The Bh+h- channels

ππ

hypothesis

πK

hypothesis

KK

hypothesisπK

hypothesis

With PID

No PID


(after all, the CKM picture of CPV does not account for the presence of matter in the Universe…)

• Some quantities very sensitive to NP are yet to be measured or lacking precise measurement

• Four examples

. arg(Vts)- via phase of Bs mixing• CKM fit prediction is very precise

2. Branching ratios of rare decays• Expect large contributions from NP models

3. Angular distributions• Sensitive to non-SM operators in interactions

4. -arg(Vub) • Tree processes assumed free of NP• Comparison with measurements from loop processes can reveal NP

Is there New Physics in B decays ??


ss from Bs J/ decays



SU(3) counterpart of Bd→J/Ks and measures the Bs- Bs mixing phase

The phase of the oscillation in the SM is given by:

sSM -2 arg (Vts) -2 = -

22~ -0.04 very small , so very sensitive to NP

Prediction from a global fit to CKM measurements (UT fit):

s = -0.037± 0.002

Recent D0 measurement:

s = -0.79±0.56(stat) (syst)

– Note: no Bs produced in B factories

+0.14- 0.01



Bs0

Bs0 Bs

0

Measure time dependent CP asymmetries

Bs(Bs)→J/ψ(μ+μ-)φ(K+K-) can proceed directly or through mixing

Need flavour taggingNeed flavour tagging

Proper time resolutionProper time resolution


High branching ratio (3x10-5), good experimental signature

Bs→J/ψ(µ+µ-) Φ(K+K-) golden channel

Final states with leptons: lepton trigger very effective for ATLAS, CMS and LHCb

However

J/ is not a pure CP eigenstateFull decay topology analysis is needed to determine CP even and CP odd states J/(CP = +1) / J/ (CP = ) (LJ/-= 0, 2 vs LJ/- = 1)

LHCb

Total

CP-even

CP-odd


Time dependent CP asymmetries in Bs, Bs J/ decays need :

1. Flavour tagging:opposite side (O.S.) : lepton, jet-charge and kaonsame side (S.S.) : “slow” kaon from the fragmentation

Bs→J/ψ(µ+µ-) Φ(K+K-) golden channel

O.S. S.S. “combined”e K Jet K

ATLAS 0.25 0.68 3.63 =4.56CMS under investigation LHCb 0.46 0.70 1.64 1.04 2.71N.N. = 7.08

eff = tag(1 2wwrong)2 [10]


Bs-Bs oscillation has to be well resolved-good that ms is not too big-resolution function must be well understood

measuring lifetimes, oscillation plot with Ds etc. Proper time resolutions

ATLAS CMS LHCb [fs] 83 77 36

NB: worse resolution =more dilution in the CPasymmetries

2.Good proper time resolution:


3. Good mass and vertex resolutions

with J/ mass constraintwithout mass constraint

ATLAS CMS LHCbm [MeV/c2] 16.5 14 14

B/S 0.25 0.33 0.12

Bs mass resolutions and Background/Signal ratios


Event yields from the “2008” run

ATLAS CMS LHCbNrec 23 k 27k 33 kNrec

eff-tag 1.0 k ? 2.3 k

Numbers of reconstructed J/ and those effectively flavour tagged


With 2008 data

ATLAS CMS LHCb(s) 0.158 ? 0.042(s)/s0.41 0.13 0.12

LHCb: BSM effect down to the level of SM can be excluded/discovered with the 2008 data

(J/, c , DsDs

can be added. No angular analysis needed, but smaller statistics)

ATLAS and CMS: (s) ≈ 0.04 with L dt = 30 fb data

By ~2013, SM prediction of s tested to a level of ~5

LHCb: stat(s) ~ 0.01 with L dt = 10 fb

Sensitivity to Φs and ΔГs

With > 2009 data


From Z. Ligeti et al hep-ph/0604112Allowed regions CL > 0.90, 0.32, 0.05

2006 with first ms

measurement

s= 0.04±0.03

0.1 0.3 0.5 hs

0.5 1.5 2.5 hs

s

s

180o

180o

90o

90o

0o

0o

LHCb, L=2fb-1LHCb, L=2fb-1

( )( )ssSMss

ssSMss

ih

ihmm

σ

σ

2exp1arg

)2exp(1

++Φ=Φ

+Δ=Δ

Allowed region

Φs : sensitivity to New Physics

• One nominal LHCb year (2 fb-1):

(s)= 0.023 ( UT fit value: -0.037)

• The measurement can be interpreted via

a parametrization of NP effects

Then ms and s can be written:


Search for rare B decays


SM expectation:BR(Bs→µ+µ-) = (3.4±0.4) x 10-9 BR(Bd→µ+µ-) = (1.0±0.5) x 10-10

World best limit by Dø: BR(Bs→µ+µ-) < 7.5 x 10-8@90%CL

In Supersymmetry:In Supersymmetry:Large contributions in some SUSY models

BR(Bd,s→µ+µ-) could be very

sensitive to high values of tan β.

Search for Bs +–

SM


Final states with leptons: lepton trigger very effective for ATLAS, CMS and LHCb

Main issue is background rejection: bX + bX

Bc± → J/ψ(µ+µ-)µ±ν

B, K, etc. BX, etc.

+ isolation in pT, etc.

ATLAS CMS LHCbm [MeV/c2] 77 36 18

Bs mass resolutions Bs

Search for Bs +–

Adressed byexcellent mass resolutionvertex resolution and particle ID


assuming the SM Br = ~3.510

ATLAS , CMS Br (B μμ) <~510 (90%CL)

LHCb: BSM contribution down to the level of SM can be excluded/discovered.

With 2008 data

Search for Bs +–

LHCb limit on BR at 90% CL (only bkg is observed)

Expected CDF+D0 Limit 2x10-8

Uncertainty in bkg predictionSM prediction

Integrated Luminosity (fb)

LHCb uses “distributions” for signal and background…


Search for Bs +–

LHCb uses “distributions” for signal and background…

ATLAS and CMS: L dt = 30 fb, <~610 (90%CL)(They plan to continue this programme at L=1034, 4 in one year)

With > 2009 data

LHCb: L dt = 10 fb, >5 observation for SM Br

Expected final (8 fb-1) from Tevatron at 90% CL : < 2·10-8


ATLAS performance summary for B

ATLAS sensitivity as a function of integrated luminosity expected to be delivered in three years after LHC start.

Integrated luminosity (fb–1)

5 observation

3 evidence

SM prediction

BR

(x1

0–9)

LHCb sensitivity(signal+bkg is observed)

Sensitivity to Bs +–

1 year @ LHCb


Sensitivity by LHCbBR(Bs→µ+µ-) in CMSSM as aFunction of gaugino mass

SM

D0 limit

10-9

10-7

10-8

10-6


Search for rare B0 K*0 decays


SM processes contributing to decay:

Decay is very sensitive to extensions of SM :Analysis of angular distributions allow to extract information

about new Physics.

BR(B0→lls) = 4.5x10-6

BR(B0→llK) = 0.5x10-6

Search for B0 K*0 decay

BR(B0→K*μ+μ-) = ~1.2 x 10-6

Decay seen in B factories, ~ no NP in BR


Transverse Asymmetry:(asymmetry in the spin amplitude of the K*)

Observables in B0 K*0μ+μ- decay

Forward-backward asymmetry AFB(s)in the rest-frame is sensitive probe of

New Physics:• Predicted zero of AFB(s) depends on

Wilson coefficients C7eff/C9

eff

K*0 polarisation can be measured

s = μμ mass squared (= q2)θl = angle between μ and B in μμ rest frame (AFB angle)


Non-MFV MSSM with

tan(β) = 5from HEP-ph/0612166

AFB(s) in SM and differentSUSY models: SUSY I = SUGRA SUSY II = MIA MSSM(from Phys.Rev.D61 (2000) 074024)

New Physics in Bd→ K0*

AT(2)

s = (m)2 [GeV2]

AFB, theory


in ATLAS and LHCb(CMS study not yet available)

for one canonical year10 fb (ATLAS) and 2fb(LHCb)

ATLAS LHCb(m) [MeV/c2] 51 14Nsignal 800 7200B/S <4.8 ~0.5

LHCb

ATLAS

4MeV/cm MeV/c

m

The B0 K*0 decays Flavour tag not necessary


+ ATLAS precision @ 30 fb-1

+ Belle 2006 SM model SM extensions

LHCb 2 fb-1(one canonical year)

By ~2013, LHCb zero crossing point with 10 fb (s0) = 0.28 (GeV/c2)2

Forward-backward asymmetry in Bd→ K0*

Zero crossing pointAFB

ATLAS 30 fb-1

s = (m)2 [GeV2]

LHCb 2 fb-1: ~7k evts B/S<0.5

determine C7eff/C9

eff with 7% stat error (SM)

σAFB (2fb-1)=1.2 GeV 2

The rare decays B±→ K±


The rare decays Bu+→K+ll

An interesting ratio

H0/A0?

Hiller & Krüger, PRD69 (2004) 074020

Corrections to unity can beLarge ~10% in models thatDistinguish between lepton flavors,like interactions involvingneutral Higgs boson


With 10 fb dataKee10 kK 19 k

By ~2013 LHCb (RK) = 0.043

The ratio RK in LHCb


Tree-level processes allow clean extraction of γ Access interference effects involving the phase between Vub and Vcb

Bs DsK B, Bd D(*)K(*), with D0 decaying to:

2 bodies: πK , KK, ππ 3 bodies: KS ππ, KS KK, KS Kπ 4 bodies: K πππ, KK ππ

Processes involving large Penguin contributions are sensitive to New Physics

Bd +– & Bs K+K–

U-spin approach

•From direct measurements with B→DK decays: γ=(83±19)° (BaBar and Belle)

LHCb can measure angle γ using various methods L0 hadron pT trigger, K/ identification: essential

The CKM angle γ in LHCb Experimental status:•From the SM fit using only indirect measurements: γ=(63.1±4.6)° (UTFit)


from Bfrom Bss D DssKK 2 time dependent asymmetries from 4 decay rates:

Bs (Bs) Ds K , D

s K

2 tree decays (b→c) and (b→u) of same magnitude interfere via Bs mixing:

large interference effects expected insensitive to new physics

CP asymmetry measures (+ s), with s being determined using Bs → J/

needs suppression of Bs Dsπ background (BR~15 higher)

DsK asymmetries (5 years, ms=20 ps–1)

Ds–K+

Ds+K–

Fit the 4 tagged, time-dependent rates: phase of D

s K = s) phase of D

s K = s) extract both and s (Bs Dsπ also used in fit to constrain other parameters like mistag rate, Δms, ΔГs)

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s

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s

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b

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Bs0{

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}K+

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}K–

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s

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b

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c

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s

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Bs0{

€

}Ds+

Expect 5400 signal events with B/S<1 at 90% CL

10° in 1year/2fb-1


from B± DK±

• “ADS+GLW” strategy:– Measure the relative rates of B– DK– and B+ DK+

decays with neutral D’s observed in final states such as: K–+ and K+–, K–+–+ and K+–+–, K+K–

– These depend on:• Relative magnitude, weak phase and strong phase between B–

D0K– and B– D0K– • Relative magnitudes (known) and strong phases between D0

K–+ and D0 K–+,and between D0 K–+–+ and D0 K–+–+

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B– ⎧ ⎨ ⎩

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}K–

colour-suppressed

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B–{

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}D0

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}K–

colour-allowed

Weak phase difference = Magnitude ratio = rB

~ 0.08

() = 5–15 with 2 fb–1


• Treat with same ADS+GLW method– So far used only D decays to K–+, K+–, K+K–

and +– final states

from B0 D0K*0

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}D0

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d

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Decay mode (+cc)2 fb–1 yield

Bbb/S

B0 (K+–)D K*0 3400 <0.3

B0 (K–+)D K*0 500 <1.7

B0 (K+K–, +–)DK*0 600 <1.4

() = 7–10 with 2 fb–1


from BDK Dalitz analyses

• B± D(KS+–)K±:– D0 and anti-D0 contributions interfere in Dalitz plot– If good online KS reconstruction: 5k signal events in 2 fb–1,

B/S < 1– Assuming signal only and flat acceptance across Dalitz plot:

() = 8 with 2 fb–1

• B± D(KK)K±:– Four-body “Dalitz” analysis– 1.7 k signal events in 2 fb–1

– Assuming signal only and flat acceptance across Dalitz plot: () = 15 with 2 fb–1


from Bfrom B and B and BssKKKK

large penguin contributions in both decays sensitive to New Physics

measure time-dependent CP asymmetry for B and BsKK

ACP(t) = Adir cos(Δmt) + Amix sin(Δmt)

Adir and Amix depend on γ, mixing phases, and ratio of penguin to tree = d eiθ

exploit “U-spin” symmetry (ds) [R.Fleischer, Phys.Lett. B459, 306 (1999)]

dππ = dKK and θππ = θKK

4 measurements and 3 unknowns, if mixing phases taken from B0J/KS and BsJ/

Expected sensitivity:

26k B , 37k BsKK, 135k BK

σ(γ) ~ 4° in 2fb-1

Bd/s

Bd/s

/K

/K

/K

/K


~ 2013 LHCb tree determination of 2.4

unaffected by BSM

DsK DK /KKADS GLW+DDalitz

( 4.5 3.6 3.6 6.7 4

LHCb performance in determination with 10 fb

With a weak assumption on U-spin symmetryCould be affected by BSM

The CKM angle γ in LHCb

ADS=Atwood,Dunietz,SonyGLW=Gronau,London,Wyler


ALICE heavy-flavour potential

• ALICE combines electronic (||<0.9),

muonic (4<<2.5),

hadronic (||<0.9) channels

HERA-LHC WorkshopCERN/LHCC 2005-014hep-ph/0601164

From A.Dainese (ALICE)

ALICE(c/b)

ATLAS/CMS(b) LHCb

(b)

-2 0 2 4 61

10

100

1 year pp 14 TeV @ nominal lumin.

pTof Q

-hadron [GeV]

ofQ-hadron

ALICE(b)(c)

ALICE(c/b)

ATLAS/CMS(b) LHCb

(b)

-46

yearpp4TeV@nominallumin.

pTof Q

- [ ]hadron GeV

ofQ-hadron

ALICE(b)(c)

•ALICE is well-equiped for heavy-flavour studies

– using several different channels / strategies– acceptance down low pt at central and forward rapidity

•With 109 events (nominal year):– ~5% statistical error on total cross sections (c and b)


Conclusions

Heavy flavour physics will play a significant role in deepening our understanding of the Standard Model, and, should New Physics be found at LHC, it provides unique tools for probing the flavour structure of the new particles

The effects of new physics loops can be seen in rare decay branching fractions and kinematic distributions and in CP-violating asymmetries in channels with very small branchingfractions

To this improvements will be fundamental better theoretical understanding and predictions


Conclusions

It is important that other approaches be followed as well:1. A Super B-Factory can, in the next decade, provide

high precision measurements as well as results complementary to those of hadronic experiments2. Rare K decay experiments 3. Searches for lepton flavor violation

The new generation of experiments at LHC , and especially LHCb, will extend the fruitful programs of the current B Factories and Tevatron


Spare slides


Impact of LHCb on UT

• LHCb (2 fb–1, 10 fb–1):– LHCb: (sin(2)) = 0.02, 0.01 () = 4.2º, 2.4º () = 10º, 4.5º

• Lattice QCD (2010, 2014):– 40, 1000 Tflop year ()/ = 2.5%, 1.5%

• Central values:– SM assumed

(just for illustration)%8.1/)(

%6.3/)(

==

10 fb–1 (2014)

2 fb–1 (2010)

%9.3/)(

%1.7/)(

==

LHCb + LQCD only

From V. Vagnoni, CKM workshop, Dec 2006


CKM matrix and the unitarity trianglesCKM matrix and the unitarity triangles

The CKM matrix is complex and unitary: V†CKM VCKM = 1

Unitarity gives relationship between rows and columns: Vij Vik* = 0 (j k)

The 6 relations can be represented as 6 unitarity triangles in the complex plane The area of each triangle corresponds to the amount of CP violation in the

transition of the quarks involved There are 6 triangles, but only 2 have sides of similar length (un-squashed)

0*** =++ tbtdcbcdubud VVVVVV

udubVV *

Re

tdtbVV *

cdcbVV *

Im

0*** =++ tbubtsustdud VVVVVV

Re

tbubVV *

tdudVV *

tsusVV *

Im

Rescale the unitarity triangles by *cbcdVV

t u b d


Precise γ determinations including processes only at tree-level, in order to disentangle possible NP contributions

Other measurements of CP phases in different channels to over-constrain the Unitarity Triangles and to search for NP contributions in loop decays

BsDsK, B0D0K*0, BDK, B0BsKK, …

B0Ks, Bs...B0B0

…

BsDs, … BsJBsJ(’)

B(s)0X B0K*0l+l-,

bsl+l-, Bs...

Search for effects of NP appearing in suppressed and rare exclusive and inclusive B decays

Precise measurement of B0s-B0

s mixing: mixing phase s and ms, s

Completing the program on B PhysicsCompleting the program on B Physics……


• ATLAS and CMS limited bandwidth for b trigger (5-10% at low L)

• ATLAS: L1 (100kHz) μ pairs or single μ (pT>6GeV) with R.O.I. em+jets info

HLT (100Hz) with r.o.i. or full scan inside inner detector: jets for hadronic channels, em for channels with e or γ, muons if a second muon is missed by L1; reconstruct intermediate resonances

• CMS: similar + partial track reco in r.o.i. and B inv mass • LHCb: L1(1MHz) is called L0(!)

μ, e,γ and h in HCAL+ pile-up system HLT (2kHz) based on alleys with partial reco

B triggers at LHC in one slide

Event type Physics

Exclusive B candidates B (core program)

High mass di-muons J/, bJ/X (unbiased)

D* candidates Charm

Inclusive b (e.g. b) B (data mining)

pT,ET

hadrons 3.8

electrons 2.8

muon 1.1

2muon 1.3

G.V. +

clara matteuzzi qcd 2007 martina franca 1 clara matteuzzi qcdworkshop martina franca, june 16–19,...

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