A. Savoy-Navarro, Korea'081 The 3 rd generation as Probes for New Physics:The CDF case Aurore...

A. Savoy-Navarro, Korea'08 1

The 3The 3rdrd generation as Probes for generation as Probes forNew Physics:The CDF caseNew Physics:The CDF case

Aurore Savoy-Navarro,UPMC-Paris/CNRS-IN2P3 France

ντ


Synopsis

• 3rd generation: WHY?

• How to detect/tag them?

• Probe for New Physics: the CDF case Some examples in:

B Physics

Top Physics

Higgs

BSM


WHY the 3rd generation?• The 3rd generation allows exploring important aspects

of Particle Physics: the

• Some key particles are made of heavy quarks (ex: the B mesons) • and/or decay into 3rd generation objects (ex: H0 but also Z0 →τ+τ-) • This decay channel may become even a dominant; ex:

τ-lepton becomes dominant in certain BSM cases (ex: also H0 if MSSM-like)• Third generation processes are backgrounds to NP (ex: top paire production…)


3rd generation objects detection has made impressive advances especially at CDF:

b-tagging & triggeringτ-tagging & triggering

but it’s quite challenging especially at hadron colliders

and challenging anyway: each member of the THIRD family has its own peculiarities

HOW TO DETECT THEM?


L00 + μvertex ISL: intermediate Si tracker Si vertex trigger: SVT

Central Outer gaseous Tracker (COT)

Plug calorimeter Part of the Muon detector

The detection of 3rd generation objects need ALL the components of a detector


Very important contribution of Tracker in CDF Trigger Architecture

L3: CPU farm Full event Reconstruction

Speed-optimized offline code

L1 pipeline

42 clock cycles

L1

L2

L2 buffer

4 events

DAQ buffers

L3 Farm

L1• 7.6 MHz Synchromous Pipeline• 5.5 μs Latency• 30 kHz accept rate

L2•Asynchromous 2 Stage Pipeline•20 μs Latency•1000 Hz accept rate

Mass Storage

(~100 Hz)

7.6 MHz Crossing rate

SVX read out after L1

SVT here

XFT here

XFT – Level 1

all trck pT>1.5 GeVσ(1/pT) = 1.7%/GeVσ(φ0) = 5 mrad96% efficiencySVT – Level 2

all trck pT>2 GeVσ(IP) = 35 μm, σ(1/Pt) = 0.3 % σ (φ0)=1 mrad

Ks

L3 plot 2001

D0

1.8 1.85 1.9 GeV/c2

800

400

0

Eve

nts

Two Track Trigger (TTT) IP>100 μm

D0

Upgrade:3D tracks

Upgrade:processing time


eXtremelyFastTracker

Good hit patterns are identified as segments, then segments are linked as tracks

XFT 3D upgrade:Add info from stereo layersFake rejection ~8

COT axial layers

COT stereo layers

Gaseous tracking chamber rebuilt from run I to run II to cope with luminosity x100 and for the first time a tracking LV1 trigger:


Upgrade SVT for luminosityUpgrade SVT for luminosity

p

event + underlying event + pile-up

p

Good Data@ higher Luminosity More Data @ lower Luminosity

Upgrade: Faster SVT components and:

32Kpatterns → 512Kpatterns new AM.

0 20 60 100 140 180 Luminosity (xE30)

original system

upgradedsystemFr

act

ion

of

ev.

Original SVT turned off above 90xE30

Upgraded SVT can run @high Lumi

At 3x1032: 5 pile ups


A dedicated new Higgs trigger & N.P. searchesA dedicated new Higgs trigger & N.P. searches

Ten orders of magnitude to fight against!! High luminosity gives largecalorimeter occupancy (pile up)that generates fake clusters/cluster merging (ex: red towersseen as one single cluster)


The upgraded Calorimeter The upgraded Calorimeter TriggerTrigger

courtesy of Simone Donati - 24x24 Calorimeter towers E(em),

E(had) sent to L2 CPU @full resolution (10

bit)- Jet, e/ clustering, MET computed

with offline-style algorithm (immune to

pileup).

- Use fixed cone algo: R=√(2 + 2)=0.7

L2Cal(4 Pulsar crates)

L2 CPU

10 bit E(em), E(had)

jet axis

Tr

The L1MET Upgrade

L2calPulsar

x6

L2CalPulsar

x6

L2CalPulsar

x6

PulsarMerger

PulsarMerger

PulsarMerger

PulsarMerger

PulsarMergerTrigger Tower

Energy(288 LVDS Cables)

Wedge Energy

L1METPulsar

Met Reconstructi

on to L1:Same L2

Resolution!

L2 PC performs clustering and Met calculation

Trigger Tower Energy

( 4 S-LINK cables)

Same Custom Hardware used to

calculate Met/SumEt for

L1

Commissioning Ongoing

Courtesy Laura Sartori

NEW!


Instantaneous Luminosity (x 1030 cm-2 s-1)

L2

Cro

ss S

ectio

n (

nb)

After L2Cal UpgradeBefore L2Cal Upgrade

Jet40L2 upgradesince Nov07

Courtesy Laura Sartori

Etmiss 25L1 commissioning

After L1 upgrade

Before L1 Upgrade

Effects of latestEffects of latesttrigger upgradestrigger upgrades on L1 and L2:on L1 and L2: 2 examples2 examples

This impacts also on the This impacts also on the

ττ- - triggerstriggers


τ+ → π+[π-π+] ντ (n π0)

BR=50%

BR=14%

An inner cone, shrinking with energy, 1 or 3 good tracks

τ IDENTIFICATION only possible in hadronic decay

Tagging and triggering based on:


Davis, LPNHE, PISA, Rutgers, TA&M installed in 2002

Primarily designed to trigger low Pt multileptons

Including τ’s


The Bs-world:

b

s

b

s

Bs0 Bs

0

MA

TTE

R

AN

TIM

ATTER

Bs observables: Δms = mH-mL≈2IM12I defines the mixing oscillation frequency

Different Lifetimes: ΔΓs=ΓL-ΓH ≈ 2 IΓ12I cos Φs

CPV: ΦsSM = arg(-M12/ Γ12) ≈ 4x10-3 rad (SM) Thus small value predicted by SM

Bs mesons = {bs} bound states

Transitions Matter ↔Antimatter via:NEW PHYSICS?

Bs sector is defined by 5 parameters:• Masses: mH, mL • Lifetimes: ΓH, Γ L (Γ=1/τ), • Phase: βs

The flavour eigenstates are linear combinations of mass and lifetimes eigenstates


ms measurementms = 17.77±0.10(stat)±0.07(syst) ps-1

Extracted parameters dominated by theoretical errors; Need more from LQCD

|Vts / Vtd|= 0.2060 ± 0.0007 (exp) +0.0081 (theo) -0.0060

CDF present focus S=H-L, (H+L)/2 and βs

1 fb-1

PR

L. 97, 242003 (2006)

(5.4 significance)

If NP occurs in mixing: Φs = ΦsSM + Φs

NP and 2βs = 2βsSM – Φs

NP standard approximation: Φs = -2βs

ALL in ONE process

βs = phase of b→ccs transition accounts for decay & mixing+decay= 2.20(SM prediction)


Flavour-tagging performance

Same tagging used successfully for mixing-frequency measurement

Opposite Side: looks at decay of the ‘other’ b-hadron in the event

Same Side: exploits the charge/species correlations with associated particles produced in hadronization of reconstructed B0

s meson

Output: decision (b-quark or antib-quark) and the probab. of being correct

OST efficiency 96 +/- 1% OST dilution: 11 +/- 2%

SST efficiency 50 +/- 1% SST dilution 27 +/- 4%

Total εD2 ~ 4%


Results

Assuming the SM, the probability of observing a fluctuation as large or larger than observed in data is 15% (1.5σ)

One dimensional: 0.16 < βs < 1.41 at 68% CL

PR

L100, 161802(2008)


Increased dataset still hints at larger than SM values!

Consistency with SM decreased 15% 7% (~1.8 σ)

(first sign of new Physics soon??)

0.28 < βs < 1.29 at 68% CL

www-cdf.fnal.gov/physics/new/bottom/080724.blessed-tagged_BsJPsiPhi_update_prelim/

3200 decays, S/B~2

ICHEP update

N.B. Analysis not yet optimized


FCNC decays forbidden at tree level, proceed through loops.FCNC decays forbidden at tree level, proceed through loops.

Higher order diagrams highly suppressed, allowing NP to manifest itself. Higher order diagrams highly suppressed, allowing NP to manifest itself.

B0d,s → μμ, B0

d,s → eμ, B0d,s → ee and D0 → μμ

LOOK for 2-body B, D rare decays at CDF:LOOK for 2-body B, D rare decays at CDF:

WHY:WHY:Ex: SM=> BR(Bs→μμ)~3.8x10-9 But BR enhanced by x10-103 by NP


B+ J/ K+

For B0d,s

B+ J/ K+

For B0d,s

B0d K+-, for

B0d,s ee, e

B0d K+-, for

B0d,s ee, e

D0

for D0 D0

for D0

Each search is relative to a normalization modeEach search is relative to a normalization mode


B ee, eμ signal after Lepton ID

mode CDF B.F. limit Previous best

B0s 4.7 (5.8) 9.4

B0d 1.5 (1.8) 3.9

B0s e 20 (26) 610

B0d e 6.4 (7.9) 9.2

B0s ee 28 (37) 5400

B0d ee 8.3 (10.6) 11.3

D0 43 (53) 13090%

(95

%)

BR

lim

its ×

108

World’s best lim

its


CDF has gained 2 orders of magnitude, now only about one order from SM


The TOP quark case

Interesting and not yet well studied case

(in progress) the top paire production

with the top decaying into τ (see next)


Search for top into τ’s : main motivations• Goal #1: First time 3 σ observation (not yet!)• Goal #2: Check BR(t→τνb) against Standard Model

– BR(WB) = 100% ? Or H+b ??

H-?

Good training camp for BSM searches

background of SUSY τ dominant decay at large tan β

Z→ττ + jets background• 1 τ→e or μ,1 τ→hadrons• Unlike the top signal:

– The 2 leptons are close– MEt points between them

OR opposite to them

• The τ ν’s energies can be reconstructed

• Veto event if it satisfies the former angular requirements and M(τ,τ) < 115 GeV

• This Z veto cuts 70% of Z→ττ and 8% of top signal

>115 GeV

CDF simulation

Other major background: QCD jets faking τ-jets


Results on 1.05 fb-1

PROCESS (1fb-1) (e, μ) + tau

Total Background 7.7 ± 1.7

SIGNAL (ttbar → l+τ) 6.4 ± 0.7

Total SM 14.1 ± 1.8

OBSERVATION 11

P-value: 8% Γ(t→τυq)/ΓSM(t→τυq) < 1.5 à 95% CL (2005 result : <5.2)

Impact of this result

Now starting study withpresentlyavailable data


Search for charged Higgs in top decaySearch for charged Higgs in top decay (cont’d)(cont’d)

Explore the possibility that t → H+b

with subsequent decay of H+ → c s Reconstruct event kinematics

Z! Top: interesting way to look for H± Z!


The many ways to produce a Higgs at CDFThe many ways to produce a Higgs at CDF

Hb,

b,_

mH<140GeV

mH>140GeV

HW(*),Z(*)

W,Z_

gg→H→bb dominates but huge QCD bkgd => close to IMPOSSIBLE

WH→lνbbZH→llbb

VH→ννbb,ν(l)bb

VH→qqbbH→ττ(+jets)

decay


Neutral SM Higgs into τ-leptons

Important to look at different decay mode (i.e. H→ττ, not

only H→ bb).

Analysis optimized for SM Higgs, but sensitive to

non SM Higgs.

MSSM predicts a much higher H-rate for large tanβ

in gg fusion, especially in τ-decay.


Search for a SUSY Higgs into 2 Search for a SUSY Higgs into 2 ττ’s’s

σ(MSSM) ~ σ(SM) x tan2β ττ signal: lower background τ-BR increases with tanβ


The many ways to search for Higgs at CDF The many ways to search for Higgs at CDF the high mass case: H→WW→lthe high mass case: H→WW→lννllνν

The physics backgrounds Analyse strategy:

0 jet events

1 jet events

≥ 2 jet events

WW/WZ

W+Jets/γ

WW/WZ

And: Drell-Yan, ttbar, single top, Multijetsall these processes are well measured


0-jet evt 1-jet evt

2+ jet evt

NN with different inputs are trained for each case Anti-b tagging is added in the ≥ 2 jets case, in order to get rid of the ttbar backgroundThe results obtained for each of these 3 cases arethen combined,

and the CDF result isand the CDF result is


CDF result on 3 fbCDF result on 3 fb-1-1 of data of data

σσ x BR (H→WW*) expected limit 1.66 times SM x BR (H→WW*) expected limit 1.66 times SM

for a Higgs mass of 165 GeV; Observed 1.63for a Higgs mass of 165 GeV; Observed 1.63

CDF & D0 combined exclude m(H0) =170 GeV at 95% CL CDF & D0 combined exclude m(H0) =170 GeV at 95% CL

(See Rob Roser’s talk)


A minimally supersymmetric world ? proposes a new symmetry

Fermions ↔ Bosons


Ex 2: SUSY Trileptons searchusing lepton+track trigger

CDF selection:

Backgrounds

Dominant if Large tan β

A. Savoy-Navarro, Korea'08 38Courtesy Sourabh Dube


100

Courtesy Sourabh Dube


Ex 2:Searches for sbottom quarkEx 2:Searches for sbottom quark • If large tan , light sbottom is expected

• Dedicated searches for b production (B.R.bb100%)

direct pair production or b from gluino decays

gg ~ 10 bb , consider region

and mass(gluino) > mass(sbottom)

Final state:

ET + 4 b-jets

~~

b

b

b~

b~g~g~

g~g~0~0~

0~0~

b

b

~

~~ ~~0~

1~~, mmmm

bt

Main background processes:- QCD-multijets- light-flavor jets tagging (“mistag”)- Top production, W/Z+jets, diboson

Predictions tested in Control Regions

B-tag algos


Exclusion limitsExclusion limitsExcluded above 0.1 pb

(M(g) ~ 350 GeV/c2)~Translated into limits on the gluino-sbottom mass

plane

Sbottom masses up to 300 GeV/c2 are excluded for M(g)<340 Gev/c2~


Ex 3: Search for RpV-SUSY Top Quarks decaying to a b-quark and a τ-lepton (all 3 in one)

Based on (only) 322 pb-1 of data collected by lepton+track triggers

Look for channels with one τ decaying leptonically and the other hadronically.

Expected 2.26+0.46-0.22 events; observed 2.


stop→τ b event

Upper limit on σ(production)

If Br(stop-->τ b) = 100%, Lower limit M(stop)i=155 GeV/c2 (assuming NLO cross-section for stop pair production). If theoretical uncertainties due toPDF's + factorisation scale taken into account, imit =151 GeV/c2


Concluding remarks: perspectives• CDF has been instrumental in developing the tools (hard-

software) to exploit the potential of the 3rd generation to tackle New Physics

• This is a particularly “high-tech Physics”: Theory, detector, analysis points of view

• Identifying these tricky objects (3rd family not and easy family…) in real time is a preriquisit especially in hadron colliders

• The future is in an heavy flavored world: LHC experiments must address very soon this issue and upgrade their detecting capacity consequently

• In this aspect also CDF is a precursor and pioneer: breakthroughs may still be expected

A. Savoy-Navarro, Korea'081 The 3 rd generation as Probes for New Physics:The CDF case Aurore...

Documents

Transcript of A. Savoy-Navarro, Korea'081 The 3 rd generation as Probes for New Physics:The CDF case Aurore...