Martina Schäfer 1

Z’ studies at LHCZ’ studies at LHC

Martina SchäferMartina Schäfer

Exotics meeting @ CERNExotics meeting @ CERN

25 25 ffebruaryebruary 2004 2004

Martina Schäfer 2

Z’ models Data used

DY and interference Total decay width

Leptonic cross section FB studies

A_FB Background

Full sim and outlook

Exotics meeting@CERN 25 february 2004Martina Schäfer 3

Z’ modelsZ’ models SSM

Z’ with same coupling constants as the usual Z

E6 models Z’=sinß Z + cosß Z Z, Z and Z

LR symetrique models =1

Z’(KK) not yet done

goal: discriminating between models

Exotics meeting@CERN 25 february 2004Martina Schäfer 4

data useddata used

Simulation with Pythia (within Athena) Z’ at 1.5TeV with complete interference structure (DY) usual Z boson DY only

without ISR/FSR cut CKIN(1)=1000

first step: analysis at generation level

channel Z’ e+e-

Exotics meeting@CERN 25 february 2004Martina Schäfer 5

DY DY and interference (1)and interference (1)

fit exp

Exotics meeting@CERN 25 february 2004Martina Schäfer 6

DY DY and interferenceand interference (2) (2)

Mll(GeV) with int.

Interference (SSM)

Mll(GeV) with int.

Mll(GeV) DY+Z’

Mll(GeV) DY+Z’

Zoom at peak

destructive narrower

broader

Exotics meeting@CERN 25 february 2004Martina Schäfer 7

total decay width (1)total decay width (1)Fit for total decay width

exp (DY)

BW

BW*exp+exp

±4 peak

DY

parton luminosity

Exotics meeting@CERN 25 february 2004Martina Schäfer 8

total decay width (2)total decay width (2)Exp. (GeV)

Theo.

(GeV)

SSM 45.9 0.3

40.5

7.9

0.09

8.0

10.0

0.09

9.0

18.5

0.12

18.0

LR 32.0

0.21

30.0

Z 2.63

0.01

2.5

DY

Exotics meeting@CERN 25 february 2004Martina Schäfer 9

cross sectioncross section calculated with

luminosity (cross section of Pythia)

number of events in the peak without DY

in 4 theoretical predictions?

* (exotics)

Exp. (fb)

*(GeV fb)

SSM 76.9

0.3

3531.4

27.0

22.8

0.1

180.9

2.2

25.9

0.1

260.5

2.7

46.7

0.2

865.0

7.0

LR 50.2

0.2

1603.2

12.6

n

(n )/(15 )

LR

Exotics meeting@CERN 25 february 2004Martina Schäfer 10

FB studiesFB studies

in pp collisions no “natural” forward -backward definition q direction “forward” q direction approximated by

Z’ boost direction in 25% of the events wrong cut in Y(Z’) at 0.8

wrong in only 10%

* = (e-,q) in Z’ rest frame

* = (e-,Z’) in Z’ rest frame

* = (e-,z-axis) in Z’ rest frame

Exotics meeting@CERN 25 february 2004Martina Schäfer 11

A_FBA_FB (1) (1)fit at cos distribution at « fixed » M

3/8(1+ cos2) + A_FB cos

Mll(GeV)

fit

fit (q<->\bar q)

counting

counting (q <-> \bar q)

counting � (without y cut)

counting

(q <-> \bar q, without y cut)

0 counting

A_FB(M)=(N+-N-)/N

N+: cos>0, at « fixed » Mor

Exotics meeting@CERN 25 february 2004Martina Schäfer 12

A_FBA_FB (2) (2)A_FB(Y)=(N+-N-)/NN+: cos>0, at « fixed » YA_FB(-Y)= - A_FB(Y) results on-peak A_FB

fit, with y cut, * = (e-,q)

SSM 0.078 0.010

0.006 0.010

-0.318 0.010

-0.049 0.010

LR 0.018 0.010

Exotics meeting@CERN 25 february 2004Martina Schäfer 13

backgroundbackground

bb 6X

pT() << 50GeV

bb

Photon and jet rejection (ET>50GeV): nomber of tracks zvertex E(calo)/p(tracking) E237/E277 , (track, cluster)

Efficency: 85% for electrons less then 0.1% for jets 4.5% for photons

Exotics meeting@CERN 25 february 2004Martina Schäfer 14

full sim and outlookfull sim and outlook

first look at full sim

work in progress Photon and jet rejection Background studies Full sim

without interference/ISR/FSR

model

1000events