1

Parton distribution function : W asymmetry

ssss

ssvvvvW

W

dudu

dududuA

WWWWA

)/()(

)/()(

ZWqq /For measurable rapidity range, |Y|<2.5, x remains within 5×10−4 < x < 5 ×10−2

With the assumption

At high Q2, gluon is dominant parton ⇨ sea quarks are generated by flavour blind g→qq splitting. Production rate is related to gluon distribution function

W and Z production : Leading order process,

Xijjiij

X dQxfQxfdxdxd ˆ),(),( 22

2121

2

Some information from Generator (W)

• Asymmetry is nearly flat over pt

• Slight dependency on pseudorapidity

3

Some information from Generator ()

• Asymmetry is nearly flat for pt (not much statistics in high pt region)

• Almost flat over the detector acceptance region (e.g., || < 2.5)

4

Variables to study

• Production rate as a function of pt and • Asymmetry as a function of Pt and • Main goal : try to choose the best pdf and constrain it’s parameters

– Is it really possible to choose the best pdf ?

• Looked events with different existing pdf in PYTHIA first

5

Comparison of different pdf : Generator W

• There is almost no difference in rate/shape• GRV94L : Statistics is low, should have been normalised

W Production rate

W Asymmetry

CTEQ5L

CTEQ3L

CTEQ5M1

GRV94L

6

Comparison of different pdf : Generator W

• There is almost no difference in rate/shape

W Production rate

W Asymmetry

7

Comparison of different pdf :Generator

• There is almost no difference in rate/shape

• Apparently, it is impossible to choose one pdf by rejecting others

Muon Production rate

Muon Asymmetry

8

Signal and backgrounds

• f + fbar' -> g + W+/- 24.65 nb

• f + g -> f' + W+/- 21.19 nb

• All these processes, where decay chains are W→τ () ~17%

• f + fbar -> Z0 1.87 nb

• f + fbar -> g + Z0 2.36 nb

• f + g -> f + Z0 1.92 nb

• g + g -> t tbar ~1 nb (Yet to look)

1. Physics backgrounds :

2. Other backgrounds :• From bottom and charm decays, but associated with jets

• From kaon and pion decay

• Other detector backgrounds

f + fbar' -> W+/- 19.54 nb Signal

9

Signals for single W→µν and Rapidity of W

• Isolated single muon

– Global muons in CMSSW

– Energy in all calorimeters due to this muon

– Energy associated with the muon

– Tracks associated with the muon

• Large missing transverse momentum

– Main difficult job is to calculate W direction from muon 4-vector . Two fold ambiguities and also need precise measurement of missing PT.

• No jetsYet to have any selection criteria, but just look at those variables and expected suggestions from you

Used private sample: Gen+Sim with _1_4_5 and Digi+Reco with 1_6_0

Preselection : || < 1.75

10

Event shape variables : Number of muons

• No, normalisation at all, just a distribution

Single W W + jet Single Z Z+ jet

→

11

Event shape variables : Pt of muon

• Use Pt > 20 GeV and also number of muon ==1

Single W W + jet Single Z Z+ jet

→

12

Event shape variables : Missing Et

• Use missing Et >20 GeV

Single W W + jet Single Z Z+ jet

→

13

Event shape variables : Eta of muon

Single W W + jet Single Z Z+ jet

→

14

Muon associated Hcal energy

• Except last on all are nearly same, which is expected

Single W W + jet Single Z Z+ jet

→

15

Tracks momentum with cone 0.5

Single W W + jet Single Z Z+ jet

→

16

Calorimeter energy within cone 0.5

• All are muon sample, thus all are nearly same

Single W W + jet Single Z Z+ jet

→

17

Event shape variables : Number of jets

• Why “Single W” events has more jets that “W+jet” ????

Single W W + jet Single Z Z+ jet

→

18

Event shape variables : Pt of jets

Single W W + jet Single Z Z+ jet

→

19

Event shape variables : Eta of jets

Single W W + jet Single Z Z+ jet

→

20

Summary

• Why LO ‘single W’ and ‘W+q/g’ has nearly same spectrum of jet (Used default Pythia setup)

• May return back to generated information

• Do not expect to select the best pdf, but need to constraint those parameters for all sets.

• Goal is for pdf, but if we can move fast, this analysis may also use in the initial stage of CMS run to establish the SM.

21

)exp()2exp(ln2

1

)exp(ln

2

12

)()(

;ln;ln2

1

ˆ),(),(

122

1

11

11

21

2121

221

221

222

2211

22

2121

WW

WW

WW

WW

bWW

WbW

bbWWW

bb

Xijjiij

X

Ys

MYxx

x

xY

Ys

Mx

M

sxY

sxExPE

xxM

ssxxExxM

ExxExxPEM

ExEExEM

PzE

PzE

PzEY

dQxfQxfdxdxd

22

Comparison of different pdf :Generator

Muon Production rate

Muon Asymmetry

23

Comparison of different pdf :Generator

• There is almost no difference in rate/shape

• Apparently, it is impossible to choose one pdf by rejecting others

Muon Production rate

Muon Asymmetry