news from delphi analyses w. adam institute of high energy physics austrian academy of sciences on...

News from DELPHI AnalysesNews from DELPHI Analyses

W. AdamInstitute of High Energy PhysicsAustrian Academy of Sciences

on behalf of the

DELPHI collaboration

LEP Jamboree, July 15th, 2003

LEP Jamboree, 15/7/03 News from DELPHI Analyses 2

StatusStatus

51 abstracts sent to EPS03 & LP03• Hadronic physics: 5• Hard QCD: 7• Heavy flavour physics: 7• Physics beyond the SM: 14• Test of the SM: 17• Detector and data handling: 1

14 papers published or accepted for publication since summer ‘02

27 drafts in review• 4 at journal• 7 at EP• 16 in internal review

Throughout the talk (unless stated otherwise):• results are preliminary• limits are at 95%CL

*After LEP shutdownThis story is purely fictional, and any resemblance to real persons and events is entirely coincidental!

© Dargaud

We are in the year 3AL*. CERN is entirely occupied by the LHC. Well, not entirely …A few small offices of indomitable LEP physicists still hold out against the invaders …


QCD & QCD & Physics Physics

Energy evolution ofevent shape distributions

Open b- and c-production

in collisions

s from event shapes

c formation in 2-photon collisions

Hadronic photon structure function

Inclusive J/ productionin 2-photon collisions

Inclusive f1 productionin Z decays

Search for b in 2-photon collisions

Masses, lifetimes and

production rates of ±

Electron structurefunction

b-quark mass effectsin the 4-jet rate

Colour reconnection in WW using particle flow and mW estimators

Correlations between particlesfrom different W bosons

mb at mZ


Open b and c Production in Open b and c Production in Collisions Collisions

Production mechanism:

Select b and c events using semi-leptonic decays:

• identify muons

• fit pt-spectrum to b,c and light quark components

651 events selected• uds normalisation fixed using fit to

hadron pt-spectra

• c normalisation fixed according to

LEP2 average (eeeeccX)

direct resolved

(eeeebbX) = 14.9 ± 3.3stat ± 3.4syst pb


Open b and c Production in Open b and c Production in … (2) … (2)

First time: use identified K to tag heavy quark flavour

• b like-sign K / (149 events)• c unlike-sign K / (171 events)

Fit c-fraction in unlike-sign sample:

Fit to like-sign sample consistent with previous result on b-production

DELPHI results confirm excess in observed b-production w.r.t. prediction

(eeeeccX) = 937 ± 191stat ± 206syst pb


Some other Some other Results Results

Inclusive J/ production in

collisions

J/ +- : selected 36 ± 7 events

c(2980) formation in collisions

Observed: c KSK, KKKK, KK

Not observed: c

Fits to mass spectrum, tot and c BRs radiative width from observed channels:

Recently CLEO, E835 and L3 have

measured lower values of .

(J/+X) = 45 ± 9stat±17syst pb

Estimated fraction from

resolved : 74 ± 22 %

pT2 = 13.9±2.0stat±1.4syst±2.7BR keV


EW MeasurementsEW Measurements

() cross section

WW cross sectionand anomalous QGCs

AbFB using inclusive

charge reconstruction

ZZ production

Single vector bosonproduction

-pair production

in collisions

WW production cross section and BRs

Mass and widthof the W boson

W polarisations

Charged TGCs

Ac,bFB using

prompt leptons

Precision EW measurementsat the Z resonance

Z* production


AAbbFBFB by Inclusive Charge Reconstruction by Inclusive Charge Reconstruction

observednumbers

asymmetry * relativesign up- / down-like

New method:• enhanced impact parameter tag

for event selection• neural networks for charge

(b / anti-b) tagging / hemisphere

AbFB to be extracted from 2 categories

of charge tagged events:

• single tag (NSfwd,N

Sbwd)

• unlike-sign double tag (NDfwd,N

Dbwd)

For each category:

Highest precision DELPHI AbFB analysis

• self calibration of key quantities• extensive study of systematics• uses also LEP1 off-peak and

LEP2 Z0 runs

Asymmetry calculated as function of• b-purity• polar angle of thrust axis• year of data taking

allows for• precise self-calibration• control of data MC• check for consistency

€

N fwd − Nbwd

N fwd + Nbwd

= AFB ⋅η ⋅p ⋅(2w −1)flavours

∑


AAbbFBFB by Inclusive Charge Reconstruction (2) by Inclusive Charge Reconstruction (2)

Enhanced b-tag uses• impact parameters & rapidities• decay vertex information

Efficiencies from data:

• b, c from # single / double tags

• correlations and uds from MC

Calibration in two steps• Careful tuning of resolutions in MC

for each year of data taking• Correction of b-tag values in MC

for c- and b-quarks, based on

measured (b-tag)

€

N fwd − Nbwd

N fwd + Nbwd


∑

fraction of events / flavour

Integrated event tag:data / MC after correction

c-efficiencies vs.hemisphere tag

(data, MC)

±1%



€

N fwd − Nbwd

N fwd + Nbwd


∑

Inclusive charge tagging / hemisphere: Neural Network using

• estimated charge / B-hadron type from probability / track

• probability for each B-hadron type• jet charge & decay vertex charge

Self-calibration from data (number of double-tagged like / unlike-sign events)

• hemisphere correlation & background correction from MC

• c charge assignment using MC + calibration from fully reconstr. D*s

dilution factor (charge assignment probability) charge assignment

probability D* data/MC

MC: correlations vs. cut



Result from simultaneous fit to AFB and b charge assignment probability

• inputs: “fwd” and “bwd” single and double tags + like-sign tags

Pole asymmetry

Main contributions to systematics:• hemisphere charge correlations• c and uds charge identification• QCD correction• detector resolution

√s (GeV) AFB stat. syst.

89.449 0.0637 ±0.0143 ±0.0017

92.231 0.0958 ±0.0032 ±0.0014

92.990 0.1041 ±0.0115 ±0.0024

€

AFB0,b = 0.0978 ± 0.0030stat ± 0.0014 syst


AAb,cb,cFBFB with prompt leptons & combination with prompt leptons & combination

Method

• using high pT & pL leptons (e,) to select semi-leptonic b- and c-decays

Inputs for b/c/background likelihoods

• pT & pL, b-tag and charge information (lepton and opposite hemisphere jet)

Asymmetries extracted by binned 2 fit to thrust and likelihoods. Pole values:

€

AFB0,b = 0.1021± 0.0052stat ± 0.0024 syst

AFB0,c = 0.0728 ± 0.0086stat ± 0.0063syst

Combination of DELPHI Ab,cFB measurements

€

AFB0,b = 0.0990 ± 0.0029

€

AFB0,c = 0.0706 ± 0.0068

(SM: 0.1036) (SM: 0.0740)


W-polarisation in eW-polarisation in e++ee--WW++WW--

Use decay angles as analyser:

Extract spin density matrix elements

using proj. operators W±’(*,*):

Assume CP-conservation:

• W-’ = W+

--’ • Im W-

’ = 0

Data sample:

• eqq’,qq’ selected by iterative discr. analysis for √s=189-208GeV

• 1880 events selected

Before extraction of SDM elements events were weighted to account for

• efficiency (typ. 70%)• purity (typ. 92%) and • migration (typ. angular resolution

0.05 in cosW, cos*; 80mrad in *)

as f(cosW,cos*,*)

need leptonic decays

€

for τ = ±1,0 : ρττ 'W −

(cosθW )∝

dσ (e+e− → W +lν )d cosθW d cosθ *dφ *

Λττ 'W −

∫ d cosθ *dφ *

*,* in W-restframe


W-polarisation in eW-polarisation in e++ee--WW++WW-- (2) (2)

SDM elements agree well withSM prediction (WPHACT):

00 differential production

cross section for WL:

averaged over e, and using both W- and W+

€

longitudinal

σ total

= (24.9 ± 3.3)%

expected : (24.0 ± 0.2)%


Single W productionSingle W production

We final states receive contributions from single W, W-pair and Zee.

Total cross section:

(assume lepton universality, =)

Need signal definition:• all t-channel diagrams, +

• W e: |cos(e1)| < 0.95,

|cos(e2)| > 0.95

• W l(l=e,): E(l) > 20 GeV

• W qq’ : M(qq’) > 45 GeV/c2

Ratio to SM / channel:

€

1.07+0.38

−0.35(stat)± 0.09(syst)

€

1.06+0.27

−0.25(stat)± 0.03(syst)

€

1.36 ± 0.18(stat)± 0.06(syst)


ZZ* Production* Production

Channels:

• eeqq, qq, qq

• 4 charged leptons• 4 quarks

“Matrix Element” signal definition

• |cosf|<0.98 4 fermions

• weight events by |MZ*|2/|Mall|

2

Final selection in bins in Mff-Mf’f’ plane

€

Zγ* = 0.137+0.029

−0.026(stat) ± 0.09(syst)pb

“LEP” signal definition: cuts on• production angle• di-fermion masses• compatibility with Z-mass


Method:• relation of densities for single-W and W-pairs (assume no correlation):

• measure for deviation: difference () or ratio (D) of left- / right-hand expression

• reference: MC predictions with LUBOEI within one (BEins) / two (BEfull) Ws

For background subtraction:• MC with BEC tuned on signal like Z0

Bose-Einstein Correlations in WW eventsBose-Einstein Correlations in WW events

€

Q = −( p1 − p2 )2

Fully hadronic WW events

Semi-leptonic WW events

€

p12WW (Q) = 2ρ p12

W + 2ρ p1W ρ p2

W = 2ρ p12W + 2ρ p12

Wmix

Mixed hadronic decays fromtwo semi-leptonic WW events:

• rotated / mirrored to balancemomentum


Bose-Einstein Correlations in WW … (2)Bose-Einstein Correlations in WW … (2)

Statistical aspects:• bins in correlated (multiple entries!)• described by covariance matrix• propagated to derived quantity D

Most pairs within one W:• use -factor & opening angle as

additional discriminants• reweight pairs acc. to purity

Fixing R to BEfull model:

€

=0.241± 0.075stat ± 0.038syst

D(Q): like-sign pairs

Fit D(Q)=N(1+e-RQ)(1+Q)

R(f

m)

Data

BEfull


MMW W - Contributions to Systematics- Contributions to Systematics

Detailed studies are underway to verify that no ALEPH-like cleaning is needed.

Summary (work in progress):• Electrons

Under control from the start of LEP2

No corrections• Soft energy flow

Complicated detailed studies.• Fragmentation

Large (well known) discrepancies

No problem for MW

• Detector effects

Small discrepancies for low energy clusters

Estimated impact order of 10MeV

Efforts concentrated around soft hadronic energy flow:

• charged energy flow

Discrepancies related to simulation of fragmentation - negligible impact

• neutral energy flow

Small differences seen, possibly due to detector effects

Final numbers and implementation of a possible correction expected in the nearest future.

Reminder: valid DELPHI number is

mW = 80.401 ±0.045stat ±0.034syst

± 0.029FSI ±0.017LEP GeV/c2


Searches: SUSY & ExoticaSearches: SUSY & Exotica

SUSY with light gravitinoand sleptons as NLSP

LSP gluino

Search for SUSY andinterpretation in MSSM

4th generation b’ quark

Anomaly mediatedSUSY breaking

SUSY withRp-violation

Single top via FCNC

+Emiss

SpontaneousRp-violation

Search for resonantsneutrino production


Search for 4Search for 4thth generation b’ quark generation b’ quark

Heavy 4th generation not excluded model with additional doublet (t’,b’)

If mb’>mZ and mb’<mt’,mt,mh :• dominant decays to cW and bZ• investigate 96<mb’<103 GeV/c2

Final states FCNC (∑BR≈81%):

• ZZ 2 l + 2 • ZZ 2 j + 2 • ZZ 4 j

Final states CC (∑BR≈90%):

• WW 2 j + l • WW 4 j

Limits on branching rations (using SM-

like for decay to heavy quarks)

b’

t’,t,c,u

W

W

Z,H,g,b’

b,s,d


Search for 4Search for 4thth generation b’ quark (2) generation b’ quark (2)

Interpretation within sequential model & extended CKM matrix• assume matrix real, ≈symmetric, ≈diagonal BRs = f(mb’,mt’,RCKM) with RCKM=|Vcb’/(Vtb’Vtb)|

• limits on CKM element ratio for two mt’-mb’ cases at limits of allowed range

lower limit from FCNC BRsupper limit from CC BRs


Searches: HiggsSearches: Higgs

Doubly charged Higgs

Neutral Higgs in MSSMbenchmark scenarios

Flavour independentneutral Higgs searches

Fermiophobic Higgs

Limits on mH and tan from a MSSM parameter scan

Charged Higgs ingeneral 2HDM

Neutral Higgs inextended models

Invisible Higgs

Neutral Higgs(SM and MSSM)


Extended MSSM neutral Higgs resultsExtended MSSM neutral Higgs results

Use all DELPHI results consistently Include contribution of H

Interpretation in 3 std. benchmarks:

• mhmax, no mixing, large

• using partial 2-loop calculations and mtop=174.3GeV/c2

Scan:

• basic grid: 1GeV/c2(mA)x0.1(tan)

• low mA: .02, .1, .25, .5, 1.5, 3GeV/c2

New LEP1 only limits• mh

max, no mixing:

Small unexcluded region at low mA and mh and tan ≈10:

• covered by limit on Znew.

mh > 44.6GeV/c2 (any tan)

mA > 44.4GeV/c2 (tan>1.7)

hZ

hA

cas

cad

es

LEP1


Extended MSSM neutral Higgs … (2)Extended MSSM neutral Higgs … (2)

mhmax no mixing

mh> 89.7 GeV/c2 > 92.0 GeV/c2

mA> 90.5 GeV/c2 > 93.0 GeV/c2

(tan > 0.4) (tan > 0.8)

Limit dependsstrongly on mtop

mhmax

no mixing

large

Exclusionincluding H


Flavour-Independent Search for h,AFlavour-Independent Search for h,A

Strategy:• design general search for

Higgs boson hadrons• reference samples: decays to gluons,

light & heavy quarks• for flavour-independent results take

most conservative assumption at each test point

Competing effects:

hZ m<40GeV/c2 m>40GeV/c2

4 jets “3-jet” likeprobabilistic

4-jet analysis

2 jet + Emiss“monojet”

likeIDA in 3

mass bins

2 jet+ee/ sequential

hA

“4 jets” High mass, mh≈mA

“3 jets”high m or low masses

“high thrust” both m < ≈40GeV/c2

gluons light quarks

efficiency mass resolution

arb. norm.


Flavour-independent Search for … (2)Flavour-independent Search for … (2)

Limits in terms of C2 = / (SM)

For individual flavours:• strange quarks:

mh > 108.0 GeV/c2 (110.6 expected)

• gluons:mh > 109.2 GeV/c2 (111.0 expected)

Limits in terms of C2

(=1 for max. allowed by EWSB)


Search for a fermiophobic HiggsSearch for a fermiophobic Higgs

General 2HDM• h can decouple from fermions• can decay to pairs of Higgs or gauge

bosons

• high BR in large parts of parameter space

• details depend on choice of potential describing H-H-couplings

Assuming SM + no couplings to ff:

hZ channel#events

(√s=183-209GeV)

qq 32 (27.2±0.4)

19 (19.5±1.1)

ll 3 (5.0±0.6)

mh > 104.1 GeV/c2 (expected: 104.6)


Search for a fermiophobic Higgs (2)Search for a fermiophobic Higgs (2)

hA production: searched for

• hA bb

• hA hhZ qq

excluded by hZ

excluded by hA

mh limit for

mA=115

mainly h , AhZ

mainly h , Abb

mainly h, Abb


ConclusionsConclusions

Physics output:• 14 publications since summer 2002• 27 drafts in pipeline• work in progress on ~ 25 other subjects

DELPHI is still a highly active collaboration!

Emphasis now on getting remaining analyses quickly to publication stage:

• many DELPHI members started second activity• tends to slow down reviewing process

You may expect many new final results at the next LEP jamboree !!!

news from delphi analyses w. adam institute of high energy physics austrian academy of sciences on...

Documents

semileptonic b decays

c production

observed bproduction

fractions of b

bproduction delphi results

c events

events c

delphi analyses4 open