status of physics analyses in aleph

Status of Physics AnalysesStatus of Physics Analysesin ALEPHin ALEPH

Günther DissertoriGünther DissertoriCERN , EP-DivisionCERN , EP-Division

on behalf of the ALEPH Collaborationon behalf of the ALEPH Collaboration

LEP Physics Jamboree, July 10 LEP Physics Jamboree, July 10 2001, 2001,

LEP Physics Jamboree, July 10, 2001

G. Dissertori 2

Status of the DetectorStatus of the Detector


G. Dissertori 3

Outlook LEP1:Outlook LEP1:

– Tau PhysicsTau Physics– Heavy Flavour PhysicsHeavy Flavour Physics– QCDQCD

LEP 1LEP 1


G. Dissertori 4

Weak Dipole Moments of the Weak Dipole Moments of the LeptonLepton

AimAim : Study the Lorentz : Study the Lorentz structure of this couplingstructure of this coupling

e+

e- -

+

??

MethodMethod : Likelihood fit : Likelihood fit (simultaneous for all couplings) to (simultaneous for all couplings) to fully differential cross section for fully differential cross section for

XeeXdd

dn

cos

Production decay : , , a120 (3)

q

m

dq

miie 55 22

av

q

m

dq

miie 55 22

av

DataData : 155 pb-1 (1990-1995) : 155 pb-1 (1990-1995) 39k events 39k events

95% CL upperlimits |Re()| |Im()|

1.05 x 10-3 2.22 x 10-3

d[e cm] 5.42 x 10-18 11.93 x 10-18


G. Dissertori 5

DataData : 1991-1995 : 1991-1995 – 4 million evts, 670k b-tagged evts4 million evts, 670k b-tagged evts

AFB0,b = 0.1009 0.0027 0.0012

sin2 W = 0.23193 0.00056

AFB0,b = 0.1009 0.0027 0.0012

sin2 W = 0.23193 0.00056

FINAL, CERN EP/2001-047

AAFBFBbb using Jet Charge using Jet Charge

AimAim :Measure :Measure

MethodMethod : inclusive measurement : inclusive measurement– b-tag via NN (30% more stat)b-tag via NN (30% more stat)– Improved jet charge tag includesImproved jet charge tag includes

fast Kaon taggingfast Kaon tagging primary+secondary vertex chargeprimary+secondary vertex charge

– lower systematics becauselower systematics because lower mistag ratelower mistag rate purities from double tag methodpurities from double tag method

bb

bb

bb

bb

totb AFB

b = -

sin2 W


G. Dissertori 6

Accepted Accepted by Phys.Lett.Bby Phys.Lett.B

xBwd = 0.716 0.006 0.006

SLD : xBwd = 0.710 0.003 0.005 0.004

xBwd = 0.716 0.006 0.006

SLD : xBwd = 0.710 0.003 0.005 0.004

b Quark Fragmentation Functionb Quark Fragmentation Function

AimAim : measure the spectrum : measure the spectrum of of xxEE = E = EBB / E / Ebeambeam

MethodMethod : semi-exclusive reconstruction : semi-exclusive reconstruction – B B D D(()) ll – 5 channels for D5 channels for D(()) decays decays

– EE from missing energy in hemisphere from missing energy in hemisphere

– Unfold raw distribution with resolution matrix from MCUnfold raw distribution with resolution matrix from MC– avoid model dependence by iterative methodavoid model dependence by iterative method

DataData : 1991 - 1995 : 1991 - 1995 4 million hadr. Z decays4 million hadr. Z decays 3400 B3400 B00 and B and B candidates candidates

bbBB


G. Dissertori 7

Inclusive b semileptonic BRInclusive b semileptonic BR

AimAim : measure the BRs : measure the BRs– BR(b BR(b X X l – BR(b BR(b c c X X l

cc

bb WW--

ll

MethodMethod : 2 analyses : 2 analyses

– b-tag b-tag OROR high p high p lepton lepton OROR

charge+impact parameter tagcharge+impact parameter tag– search for lepton (e, search for lepton (e, ) in ) in

opposite hemisphereopposite hemisphere improved dE/dx (TPC pads)improved dE/dx (TPC pads)

– A) fit pA) fit p spectrum spectrum

– B) measure charge correlationB) measure charge correlation

DataData : 1991 - 1995 : 1991 - 1995– combine results a) and b) combine results a) and b)

BR (b X l ) = 0.1070 0.0010 0.0024 0.0025model

BR (b c X l ) = 0.0818 0.0015 0.0023 model

BR (b X l ) = 0.1070 0.0010 0.0024 0.0025model

BR (b c X l ) = 0.0818 0.0015 0.0023 model

0008.00012.0

Sending to journal

Statistical errors only


G. Dissertori 8

ss and QCD Colour factors and QCD Colour factors

2

2

2

s

s

s

CF

CA

nfTF

QCD : SU(3) CF=4/3, CA=3, TF=1/2

AimAim : measure simultaneously : measure simultaneously the strong coupling and the QCD the strong coupling and the QCD colour factors using colour factors using 4-jet evts4-jet evts

MethodMethod : Fit : Fit NLONLO predictions to 4-jet predictions to 4-jet observables observables – RR44 (y (ycutcut) )

– four angular correlations in 4-jet eventsfour angular correlations in 4-jet events Bengtsson-Zerwas angle, …Bengtsson-Zerwas angle, …

DataData : 1994 - 1995 : 1994 - 1995 2.5 million hadr. Z decays2.5 million hadr. Z decays 163k 4-jet evts (y163k 4-jet evts (ycutcut = 0.008) = 0.008)

ss(M(Mzz) = 0.119 ) = 0.119 0.006 0.006 0.022 0.022

CCAA = 2.93 = 2.93 0.14 0.14 0.49 0.49

CCFF = 1.35 = 1.35 0.07 0.07 0.22 0.22

ss(M(Mzz) = 0.119 ) = 0.119 0.006 0.006 0.022 0.022

CCAA = 2.93 = 2.93 0.14 0.14 0.49 0.49

CCFF = 1.35 = 1.35 0.07 0.07 0.22 0.22


G. Dissertori 9

ss and QCD Colour factors... and QCD Colour factors...

Using all variablesUsing all variables Using only angular correlations +Using only angular correlations +assuming standard hadronization corrections!assuming standard hadronization corrections!

Massless gluino at NLO!


G. Dissertori 10

ss from Event Shapes from Event Shapes

AimAim : measure : measure ss from fit of from fit of NLO+resummed QCDNLO+resummed QCD predictions predictions to event shape distributionsto event shape distributions

MethodMethod : from hadronic Z decays : from hadronic Z decays

– Thrust, -lnyThrust, -lny33, M, Mhh, C, Cparpar, B, Btottot, B, Bww

– at LEP1 at LEP1 andand LEP2 LEP2

– hadronization corrections from hadronization corrections from

MCMC

– consistent treatment of consistent treatment of

systematic errors at all energiessystematic errors at all energies

)ln()()(1 2 yfyByA

dy

d mnsss

had

DataData : combined fit to 91 - : combined fit to 91 - 207 GeV207 GeV ss(M(MZZ) = 0.1203 ) = 0.1203 0.001 0.001 0.0013 0.0013

0.00460.0046theotheo

ss(M(MZZ) = 0.1203 ) = 0.1203 0.001 0.001 0.0013 0.0013 0.00460.0046theotheo


G. Dissertori 11

Outlook LEP2:Outlook LEP2:

– WW (FSI)WW (FSI)– Exotics : Exotics :

anomalous couplingsanomalous couplings single topsingle top

– ““Standard exotics”:Standard exotics”: SUSYSUSY HiggsHiggs

LEP 2LEP 2


G. Dissertori 12

Bose-Einstein Correlations in WW Bose-Einstein Correlations in WW eventsevents

AimAim : look for BE correlations : look for BE correlations between pions from different Wsbetween pions from different Ws

WW11WW22

BE?BE?

BE?BE?

BEBE BEBE

MethodMethod : measure the observable : measure the observable

– mixedmixed hadronic parts of different semi-leptonic evts hadronic parts of different semi-leptonic evts

22

BE no MC,mixedhadr

Bkgr -DATA mixedhadr

Ep Q

QQ

QQ

22

BE no MC,mixedhadr

Bkgr -DATA mixedhadr

Ep Q

QQ

QQ

DataData : 183 - 208 GeV : 183 - 208 GeV

Q(GeV)Q(GeV)

Confirms our previous results:Confirms our previous results:

BE correlations between pions from different Ws BE correlations between pions from different Ws are disfavouredare disfavoured


G. Dissertori 13

Particle Flow in WW eventsParticle Flow in WW events

AimAim : look for colour : look for colour reconnection effects in fully reconnection effects in fully hadronic WW evtshadronic WW evts

WW22

DD

CCBB

WW11AA

MethodMethod : apply the same : apply the same selection as for W mass analysisselection as for W mass analysis– project chg+neutral particles

into planes between jets from Ws– compute the ratio of particle flow

in different interjet regions

DataData : 189 - 207 GeV : 189 - 207 GeV

– compare to predictions of compare to predictions of different MC modelsdifferent MC models

– check SKI for different Kcheck SKI for different Kii values values

Minimum at Ki 3.570% CR at 189 GeV.

Systematics under study

Ki

2


G. Dissertori 14

Reduction in FSI uncertainty on Reduction in FSI uncertainty on MMWW? ?

AimAim : Make W mass analysis in : Make W mass analysis in fully hadronic channel more robust fully hadronic channel more robust w.r.t. colour reconnection effectsw.r.t. colour reconnection effects

– b) b) cut outcut out particles which particles which lie in interjet region lie in interjet region are soft are soft

MethodMethod : : – a) apply a) apply cone jet algorithmcone jet algorithm in in

order to recompute jet directionsorder to recompute jet directions study dependence on study dependence on cone size Rcone size R

e.g. expected for R=0.75 reduction by a factor of 2 in mW, with 13% increase in statistical uncertainty

e.g. expected for R=0.75 reduction by a factor of 2 in mW, with 13% increase in statistical uncertainty

Mass shifts vs R

0

0.025

0.05

0.075

0.1

0.125

0.15

0.5 1 1.5 2

R (rad)

m

W (

GeV

)

SK1 k=0.65

SK1 100%

Herwig CR

Durh

am

mm

W(G

eV

/c2)


G. Dissertori 15

Anomalous Neutral CouplingsAnomalous Neutral Couplings

AimAim : look for anomalous contr. : look for anomalous contr.– in SM forbidden at tree levelin SM forbidden at tree level– model them by anomalous vertex contributions model them by anomalous vertex contributions

hh,Z,Z1,..,41,..,4

MethodMethod : same topology as radiative : same topology as radiative returnsreturns– 2 jets + isolated photon2 jets + isolated photon

– measure cross section, cos (measure cross section, cos (), angle(), angle(--jets)jets)

– likelihood including anomalous couplingslikelihood including anomalous couplings

e+

e-

q

q

Z*,*

Z

DataData : 189-207 GeV , >600 pb : 189-207 GeV , >600 pb-1 -1 no deviation from SM observedno deviation from SM observed


G. Dissertori 16

Single Top ProductionSingle Top Production

AimAim : look for FCNC : look for FCNC– in SM only via loops in SM only via loops <10<10-9-9 fb fb– model FCNC by anomalous vertex contributionsmodel FCNC by anomalous vertex contributions

MethodMethod : depending on W decay from t : depending on W decay from t bW, search forbW, search for– W W qq’ : qq’ : 4 jet topology 4 jet topology – W W ll 2 jets + isolated lepton2 jets + isolated lepton– tag the b-jettag the b-jet– mmtoptop dependence dependence reduced by re- reduced by re-

optimizationoptimization

e+

e- t

c/u

DataData : 189-207 GeV , 625 pb : 189-207 GeV , 625 pb-1 -1 no significant excess observedno significant excess observed


G. Dissertori 17

Impact of Higgs searches on LSP Impact of Higgs searches on LSP limitlimit

AimAim : study impact of Higgs : study impact of Higgs searches on m(LSP) limit searches on m(LSP) limit

DataData : take limits on m : take limits on mhh<113.5 GeV/c<113.5 GeV/c22 as well as MSSM scan as well as MSSM scan

tan

m(L

SP)

m(LSP)

MethodMethod : radiative corr. to Higgs : radiative corr. to Higgs

mass = mass = f(log(mf(log(mstopstop/m/mtoptop), tan), tan))

– limit on mlimit on mhh limit on limit on mmstopstop vs vs

tantan limit on limit on MM2 2 vs tanvs tan for fixed for fixed

mm00 improve limit improve limit m(LSP) vs tanm(LSP) vs tan

– small msmall m00 m = m m = m no sensitivity no sensitivity

(corridor)(corridor) but small mbut small m00 small slepton masses small slepton masses

~~


G. Dissertori 18

Impact of stau mixing on LSP limitImpact of stau mixing on LSP limit

AimAim : avoid drop in m(LSP) limit : avoid drop in m(LSP) limit for large stau mixingfor large stau mixing

small mixing large

)tan(

1,~

2,~

2,~

~

m

m

AmmM

R

L

MethodMethod :design dedicated searches for :design dedicated searches for

– tau final statestau final states

– ““invisible” final statesinvisible” final states

– for for large tanlarge tan, deep gaugino region, deep gaugino region

DataData : 189 - 208 GeV : 189 - 208 GeV

Chargino+selectron incl incl (ISR analysis)

...~~ 01

01

02

~

No mixingNo mixing maximal mixingmaximal mixing

Stau mixing angle


G. Dissertori 19

Status of the SM Higgs SearchStatus of the SM Higgs Search

Results published in Results published in PLB 495 (2000) 1 : 3PLB 495 (2000) 1 : 3 excess excess– 2 independent analysis streams. Analyses frozen before data taking!2 independent analysis streams. Analyses frozen before data taking!

During last months following developmentsDuring last months following developments

– Additional MC Additional MC more precise shapes and efficienciesmore precise shapes and efficiencies

– all Y2K data reprocessed in December 2000 (gained all Y2K data reprocessed in December 2000 (gained 1pb 1pb-1-1)) NOTENOTE : : 3 most significant candidates were already reprocessed 3 most significant candidates were already reprocessed

before the publication, showing that they are stablebefore the publication, showing that they are stable

– New LEP ENew LEP ECM CM (about 140 MeV lower)(about 140 MeV lower)

– improved treatment of improved treatment of beam-induced backgroundbeam-induced background studied on random triggers, “dirty MC” generated, cleaning studied on random triggers, “dirty MC” generated, cleaning

procedure implementedprocedure implemented

– further systematic studiesfurther systematic studies evaluated evaluated impact of uncertaintiesimpact of uncertainties from b-tagging, correlations in from b-tagging, correlations in

discriminating variables, jet smearing, gluon splitting, discriminating variables, jet smearing, gluon splitting, ss, MC , MC description of selection variables description of selection variables on (1-CLon (1-CLbb))


G. Dissertori 20

Status of the SM Higgs Search...Status of the SM Higgs Search...

Outcome :Outcome :

The effects of recent changes and of systematic uncertainties are within 0.2

as estimated in our publication

The effects of recent changes and of systematic uncertainties are within 0.2

as estimated in our publication

We are very close to publishing our final paper on this We are very close to publishing our final paper on this topic...topic...


G. Dissertori 21

SummarySummary

Plenty of (preliminary and final) physics results Plenty of (preliminary and final) physics results

using data collected by ALEPH at LEP1 and LEP2.using data collected by ALEPH at LEP1 and LEP2.

Extensive work put into the Extensive work put into the studies of systematic studies of systematic

uncertainties of the SM Higgs searchuncertainties of the SM Higgs search– result is stable. result is stable. Final publication to come soon. Final publication to come soon.

For more details, have a look atFor more details, have a look at

http://alephwww.cern.ch/ALPUB/oldconf/summer01/http://alephwww.cern.ch/ALPUB/oldconf/summer01/

summer.htmlsummer.html

status of physics analyses in aleph

Documents

jet evts qcd

jet chargeaim

statimproved jet charge

qcd colour factorsaim

jet directionsstudy

cone jet algorithm

ww eventsaim

colour reconnection