Äîêóìåíò âçÿò èç êýøà ïîèñêîâîé ìàøèíû. Àäðåñ îðèãèíàëüíîãî äîêóìåíòà : http://qfthep.sinp.msu.ru/talks2013/GorbunovAfb.pdf Äàòà èçìåíåíèÿ: Mon Jun 24 14:12:32 2013 Äàòà èíäåêñèðîâàíèÿ: Thu Feb 27 20:12:20 2014 Êîäèðîâêà: ISO8859-5 Ïîèñêîâûå ñëîâà: m 20

Study of the Drell-Yan process with CMS.
QFTHEP 2013: XXIth International Workshop High Energy Physics and Quantum Field Theory , 23-30 Jun 2013, Saint Petersburg, Saint Petersburg (Russian Federation)

I. Gorbunov, On behalf of the CMS Collaboration
JINR, Dubna

June 24, 2013

I. Gorbunov Ilya.Gorbunov@cern.ch

Study of the Drell-Yan process with CMS.

1/23


CMS Detector

Global muon momentum resolution: dpT /pT = 1 - 1.5% at pT = 10 GeV , dpT /pT = 6 - 17% at pT = 1 TeV Electron energy resolution: dE /E < 0.5% fro E > 100 GeV
I. Gorbunov Ilya.Gorbunov@cern.ch Study of the Drell-Yan process with CMS. 2/23


Measurement of the Drell-Yan Cross Section in pp Collisions at s = 7 TeV
Based On: CMS-PAS-SMP-13-003

I. Gorbunov Ilya.Gorbunov@cern.ch

Study of the Drell-Yan process with CMS.

3/23


The Drell-Yan process
The production of lepton pairs in pp-collisions is described by the s-channel exchange of Z Theoretical calculations of d /dM (ll ) and d 2 /dM (ll )Y (M (ll ) - dilepton invariant mass, Y - dilepton rapidity) established up to NNLO order Comparison of Data and MC provide stringent tests of QCD and Measurements are done at s = 7 TeV significant constraints on the on CMS data correstponding to evaluation PDFs L = 4.5 fb-1 (dimuon) and DY is a mojor background for t ? L = 4.8 fb-1 (dielectron) in t and diboson measurements as well 20 < M (ll ) < 1500 GeV range, results as for searches for new physics are normalized to the cross section in (high mass dilepton resonances) the Z region (60 < M (ll ) < 120 GeV )
I. Gorbunov Ilya.Gorbunov@cern.ch Study of the Drell-Yan process with CMS. 4/23


DY Cross Section

Cross sections are calculated as = Nu A L (1)

where Nu is the unfolded background-subtracted yield and A acceptance, - efficiency (estimated from simulation). - factor that accounts for differences in the efficiency between data and simulation. L is not required for the measurements since the cross sections are normalized to the Z region.

I. Gorbunov Ilya.Gorbunov@cern.ch

Study of the Drell-Yan process with CMS.

5/23


Muon Selection
Dimuon trigger with minimum pT threshold One muon with | | < 2.4 and pT > 14 GeV and one with pT > 9 GeV Standart CMS muon identification and quality criteria (number of hits etc.) Impact parameter in the transverse plane less then 2mm Angle between the two muons must differ from by more than 5 mrad Dimuon vertex 2 probability smaller than 2%. Isolation of both muons Irel = ( pT (tracks ) + ET (had ))/pT (Å) < 0.15, where ET (had ) - sum of the ET of hadronic deposits and pT (tracks ) sum of the pT of the additional tracker tracks in cone R = ()2 + ( )2 < 0.3
I. Gorbunov Ilya.Gorbunov@cern.ch Study of the Drell-Yan process with CMS. 6/23


Electron Selection
Dielectron trigger with ET threshold 17 GeV for one of the electrons and 8 GeV for the other Candidate is required to be consistent with a particle originating from the primary vertex Electron identification criteria based on shower shape and track-cluster matching are applied No missing hits in the pixel detector Eliminating those electrons for which a partner track consistent with a conversion hypothesis is found Isolation ( pT (tracks ) + ET (had ) + ET (em))/pT (e ) < 0.15, where ET (em) is the sum of the ET of electromagnetic deposits, except for electrons with ET < 20 GeV where requirement is less than 0.1 | | < 1.44 or 1.57 < | | < 2.5 Electron ET > 10 GeV
I. Gorbunov Ilya.Gorbunov@cern.ch Study of the Drell-Yan process with CMS. 7/23


Acceptance and Efficiency

1 0.8 0.6 0.4

*/Z ÅÅ

at s = 7 TeV, CMS Simulation

1 0.8 0.6 0.4

*/Z ee

at s = 7 TeV, CMS Simulation

A

A

0.2 0 15

Aç

0.2 0 15

Aç

30

60

120

M(ÅÅ) (post-FSR) [GeV]

240

600

1500

30

60

120

240

600

1500

M(ee) (post-FSR) [GeV]

DY acceptance (blue, filled circles), efficiency (red, open triangles), and their product (black, open squares) per invariant mass bin, for the mu + mu - (left) and e + e - (right) channels

I. Gorbunov Ilya.Gorbunov@cern.ch

Study of the Drell-Yan process with CMS.

8/23


Background 1
entries per bin
107 106 105 104 103 102 10 1
4.5 fb-1 at s = 7 TeV

CMS Preliminary
data */Z ÅÅ */Z EWK tt+tW+tW QCD

entries per bin

108

108 107 106 105 104 103 102 10 1
4.8 fb-1 at s = 7 TeV

CMS Preliminary
data */Z ee */Z EWK QCD tt+tW+tW

data/MC

data/MC

1.5 1 0.5 15

30

60

120

240

M(ÅÅ) [GeV]

600

1500

1.5 1 0.5 15

30

60

120

240

600

1500

M(ee) [GeV]

The observed dimuon (left) and dielectron (right) invariant mass spectra within the detector acceptance for data and Monte Carlo events and corresponding data to MC ratio of yields. The FEWZ-POWHEG correction is applied to the Monte Carlo signal events. Electron energy correction is applied to data and simulated events. QCD and ttbar background yields as predicted by data-driven methods.
I. Gorbunov Ilya.Gorbunov@cern.ch Study of the Drell-Yan process with CMS. 9/23


Background 2
entries per bin entries per bin entries per bin
10000
CMS Preliminary, 4.5 fb
-1

16000
CMS Preliminary, 4.5 fb
-1

at s = 7 TeV, 20 < M < 30 GeV

at s = 7 TeV, 30 < M < 45 GeV

8000 CMS Preliminary, 4.5 fb -1 at s = 7 TeV, 45 < M < 60 GeV 7000 6000 5000 4000 3000 2000 1000 0
DATA */Z ÅÅ */Z EWK tt+tW+tW QCD

8000

6000

DATA */Z ÅÅ */Z EWK tt+tW+tW QCD

14000 12000 10000 8000

DATA */Z ÅÅ */Z EWK tt+tW+tW QCD

4000

6000 4000

2000 2000 0
data/MC data/MC
1.2 1.1 1 0.9 0.8 0.7 1.2 1.1 1 0.9 0.8 0.7

data/MC 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4

1.3

1.3

1.3 1.2 1.1 1 0.9 0.8 0.7

0

0.2 0.4 0.6 0.8

1

1.2 1.4 1.6 1.8

2

2.2 2.4

0

0

0.2 0.4 0.6 0.8

1

1.2 1.4 1.6 1.8

2

2.2 2.4

Dimuon Rapidity, |Y(ÅÅ)|

Dimuon Rapidity, |Y(ÅÅ)|

Dimuon Rapidity, |Y(ÅÅ)|

entries per bin

entries per bin

160 140 120 100 80 60 40 20 0

CMS Preliminary, 4.5 fb-1 at s = 7 TeV, 60 < M < 120 GeV

2000 1800 1600 1400 1200 1000 800 600

entries per bin

ç10
DATA */Z ÅÅ */Z EWK tt+tW+tW QCD

CMS Preliminary, 4.5 fb -1 at s = 7 TeV, 120 < M < 200 GeV

800 700 600 500 400 300 200

CMS Preliminary, 4.5 fb

-1

at s = 7 TeV, 200 < M < 1500 GeV

DATA */Z ÅÅ */Z EWK tt+tW+tW QCD

DATA */Z ÅÅ */Z EWK tt+tW+tW QCD

400 200 0
1.5 1.4 1.3 1.2 1.1 1 0.9 0.8 0.7 0.6 0.5

100 0
1.5 1.4 1.3 1.2 1.1 1 0.9 0.8 0.7 0.6 0.5

data/MC

data/MC

1.2 1.1 1 0.9 0.8 0.7

0

0.2 0.4 0.6 0.8

1

1.2 1.4 1.6 1.8

2

2.2 2.4

0

0.2 0.4 0.6 0.8

1

1.2 1.4 1.6 1.8

2

2.2 2.4

data/MC

1.3

0

0.2 0.4 0.6 0.8

1

1.2 1.4 1.6 1.8

2

2.2 2.4

Dimuon Rapidity, |Y(ÅÅ)|

Dimuon Rapidity, |Y(ÅÅ)|

Dimuon Rapidity, |Y(ÅÅ)|

The observed dimuon rapidity spectra per invariant mass slice for data and Monte Carlo events.
I. Gorbunov Ilya.Gorbunov@cern.ch Study of the Drell-Yan process with CMS. 10/23


Normalized rapidity-invariant mass spectrum
1/Z d/d|Y(ÅÅ)| 1/Z d/d|Y(ÅÅ)|
0.06
CMS Preliminary, 4.5 fb-1 at s = 7 TeV, 20 < M(ÅÅ ) < 30 GeV
Data ( Å)

0.04 0.035 0.03 0.025 0.02 0.015

1/Z d/d|Y(ÅÅ)|

CMS Preliminary, 4.5 fb-1 at s = 7 TeV, 45 < M(ÅÅ ) < 60 GeV
Data ( Å)

0.012

CMS Preliminary, 4.5 fb-1 at s = 7 TeV, 120 < M(ÅÅ) < 200 GeV Data ( Å)

0.05

0.01
FEWZ+CT10 NLO

FEWZ+CT10 NLO

FEWZ+CT10 NLO

0.04

FEWZ+CT10 NNLO

FEWZ+CT10 NNLO

0.008

FEWZ+CT10 NNLO

0.03

0.006

0.02 0.01 0.01

0.004

0.002 0.005 0
1.7 1.6 1.5 1.4 1.3 1.2 1.1 1 0.9 0.8

0
data/theory data/theory
1.4 1.3 1.2 1.1 1 0.9 0.8

0
data/theory
1.5 1.4 1.3 1.2 1.1 1 0.9 0.8 0.7

0

0.2 0.4 0.6 0.8

1

1.2 1.4 1.6 1.8

2

2.2

2.4

0

0.2 0.4 0.6 0.8

1

1.2 1.4 1.6 1.8

2

2.2

2.4

0

0.2 0.4 0.6 0.8

1

1.2 1.4 1.6 1.8

2

2.2

2.4

Dimuon Rapidity, |Y(ÅÅ)|

Dimuon Rapidity, |Y(ÅÅ)|

Dimuon Rapidity, |Y(ÅÅ)|

1/Z d/d|Y(ÅÅ)|

1/Z d/d|Y(ÅÅ)|

1.2
CMS Preliminary, 4.5 fb-1 at s = 7 TeV, 60 < M(ÅÅ) < 120 GeV
Data ( Å)

1/Z d/d|Y(ÅÅ)|

0.09 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0
data/theory

CMS Preliminary, 4.5 fb-1 at s = 7 TeV, 30 < M(ÅÅ ) < 45 GeV
Data ( Å)

0.002

CMS Preliminary, 4.5 fb-1 at s = 7 TeV, 200 < M(ÅÅ) < 1500 GeV Data ( Å)

1

0.0018 0.0016 0.0014

FEWZ+CT10 NLO

FEWZ+CT10 NLO

FEWZ+CT10 NLO

0.8
FEWZ+CT10 NNLO

FEWZ+CT10 NNLO

FEWZ+CT10 NNLO

0.0012 0.001

0.6 0.0008 0.0006 0.2 0.0004 0.0002 0
data/theory data/theory
1.3 1.2 1.1 1 0.9 0.8

0.4

0
1.4 1.3 1.2 1.1 1 0.9 0.8

1.2 1.1 1 0.9 0.8

0

0.2 0.4 0.6 0.8

1

1.2 1.4 1.6 1.8

2

2.2

2.4

0

0.2 0.4 0.6 0.8

1

1.2 1.4 1.6 1.8

2

2.2

2.4

0

0.2 0.4 0.6 0.8

1

1.2 1.4 1.6 1.8

2

2.2

2.4

Dimuon Rapidity, |Y(ÅÅ)|

Dimuon Rapidity, |Y(ÅÅ)|

Dimuon Rapidity, |Y(ÅÅ)|

The Drell-Yan rapidity-invariant mass spectrum in detector acceptance, normalized to the Z resonance region, r = 1/Z d 2 /dMdY .
I. Gorbunov Ilya.Gorbunov@cern.ch Study of the Drell-Yan process with CMS. 11/23


Comparison with theory expectations
1/ Z d/d|Y(ÅÅ)| 1/ Z d/d|Y(ÅÅ)|
0.045 0.04 0.035 0.03 0.025
Data (Å )

1/ Z d/d|Y(ÅÅ)|

CMS Preliminary, 4.5 fb-1 at s = 7 TeV, 20 < M(ÅÅ ) < 30 GeV

CMS Preliminary, 4.5 fb-1 at s = 7 TeV, 45 < M(ÅÅ ) < 60 GeV

CMS Preliminary, 4.5 fb-1 at s = 7 TeV, 120 < M(ÅÅ) < 200 GeV

0.025

0.008 0.007 0.006 0.005

0.02

0.015

Data (Å ) FEWZ+CT10 NNLO FEWZ+NNPDF2.1 NNLO FEWZ+MSTW2008 NNLO FEWZ+CT10W NNLO FEWZ+JR09 NNLO

0.02 0.015 0.01 0.005
data/theory
1.3 1.2 1.1 1 0.9 0.8 0.7

FEWZ+CT10 NNLO FEWZ+NNPDF2.1 NNLO FEWZ+MSTW2008 NNLO FEWZ+CT10W NNLO FEWZ+JR09 NNLO FEWZ+ABKM NNLO FEWZ+HERA NNLO
data/theory

0.004 0.003 0.002 0.001 0 1.5 1.4 1.3 1.2 1.1 1 0.9 0.8 0.7 0.6 0.5
data/theory

Data (Å ) FEWZ+CT10 NNLO FEWZ+NNPDF2.1 NNLO FEWZ+MSTW2008 NNLO FEWZ+CT10W NNLO FEWZ+JR09 NNLO FEWZ+ABKM NNLO FEWZ+HERA NNLO

0.01

0.005

FEWZ+ABKM NNLO FEWZ+HERA NNLO

0 1.3
1.2 1.1 1 0.9 0.8 0.7

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

2.2

2.4

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

2.2

2.4

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

2.2

2.4

Dimuon Rapidity, |Y(ÅÅ)|

Dimuon Rapidity, |Y(ÅÅ)|

Dimuon Rapidity, |Y(ÅÅ)|

1/ Z d/d|Y(ÅÅ)|

1/ Z d/d|Y(ÅÅ)|

1/ Z d/d|Y(ÅÅ)|

0.0016
CMS Preliminary, 4.5 fb-1 at s = 7 TeV, 200 < M(ÅÅ) < 1500 GeV

CMS Preliminary, 4.5 fb-1 at s = 7 TeV, 30 < M(ÅÅ ) < 45 GeV

CMS Preliminary, 4.5 fb-1 at s = 7 TeV, 60 < M(ÅÅ) < 120 GeV

0.06

0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 1.3
1.2 1.1 1 0.9 0.8 0.7

0.0014 0.0012 0.001 0.0008 0.0006 0.0004 0.0002 0 1.5 1.4 1.3 1.2 1.1 1 0.9 0.8 0.7 0.6 0.5
Data (Å ) FEWZ+CT10 NNLO FEWZ+NNPDF2.1 NNLO FEWZ+MSTW2008 NNLO FEWZ+CT10W NNLO FEWZ+JR09 NNLO FEWZ+ABKM NNLO FEWZ+HERA NNLO

0.05

0.04
Data (Å ) FEWZ+CT10 NNLO FEWZ+NNPDF2.1 NNLO FEWZ+MSTW2008 NNLO FEWZ+CT10W NNLO FEWZ+JR09 NNLO

0.03

Data (Å ) FEWZ+CT10 NNLO FEWZ+NNPDF2.1 NNLO FEWZ+MSTW2008 NNLO FEWZ+CT10W NNLO FEWZ+JR09 NNLO FEWZ+ABKM NNLO FEWZ+HERA NNLO

0.02

0.01

FEWZ+ABKM NNLO FEWZ+HERA NNLO

data/theory

data/theory

1.2 1.1 1 0.9 0.8 0.7

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

2.2

2.4

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

2.2

2.4

data/theory

0 1.3

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

2.2

2.4

Dimuon Rapidity, |Y(ÅÅ)|

Dimuon Rapidity, |Y(ÅÅ)|

Dimuon Rapidity, |Y(ÅÅ)|

Comparison with theory expectations with various NNLO PDF sets: CT10, HERA, NNPDF2.1, MSTW08, CT10W, JR09, ABKM.
I. Gorbunov Ilya.Gorbunov@cern.ch Study of the Drell-Yan process with CMS. 12/23


Normalized invariant mass spectrum
CMS Preliminary CMS Preliminary

1/Z d/dM(ÅÅ) [GeV-1 ]

1 10-1 10-2 10
-3

4.5 fb-1 at

1/Z d/dM(ee) [GeV-1 ]

s = 7 TeV

1 10-1 10-2 10
-3

4.8 fb-1 at

s = 7 TeV

*/Z ÅÅ

*/Z ee

10-4 10-5 10-6 10-7 10
-8

10-4 10-5 10-6

Data (Å Å , 4.5 fb-1 in 2011) NNLO, FEWZ+CT10 NNLO, FEWZ+CT10 (with EWK correction unc.)

10-7 10
-8

Data (ee, 4.8 fb-1 in 2011) NNLO, FEWZ+CT10 NNLO, FEWZ+CT10 (with EWK correction unc.)

10-9

10-9

data/theory

1.5 1 0.5

M(ÅÅ) [GeV]

data/theory

1.5 1 0.5

M(ee) [GeV]

15

30

60

120

240

M(Å Å ) [GeV]

600

1500

15

30

60

120

240

600

1500

M(ee) [GeV]

The Drell-Yan invariant mass spectrum in the dimuon (left) and dielectron (right) channel, normalized to the Z region, r = 1/Z d /dM , as measured and as predicted by NNLO, for the full phase space.

I. Gorbunov Ilya.Gorbunov@cern.ch

Study of the Drell-Yan process with CMS.

13/23


Combined DY invariant mass
CMS Preliminary

1/Z d/dM(ee) [GeV-1 ]

1 10-1 10-2 10-3 10-4 10-5 10-6 10-7 10-8 10-9

4.8 fb at

-1

s = 7 TeV

*/Z ee

Data (ee, 4.8 fb-1 in 2011) NNLO, FEWZ+CT10 NNLO, FEWZ+CT10 (with EWK correction unc.)

data/theory

1.5 1 0.5

M(ee) [GeV]

15

30

60

120

240

600

1500

M(ee) [GeV]

The Drell-Yan invariant mass spectrum in the combined channel, normalized to the Z region, r = 1/Z d /dM (NNLO).
I. Gorbunov Ilya.Gorbunov@cern.ch Study of the Drell-Yan process with CMS. 14/23


AFB and the Drell-Yan process
Vector and axial-vector currents in the process q q Z / l + l - lead to ? P-symmetry breaking and forward-backward asymmetry (AFB ) in the number of Drell-Yan lepton pairs:
AFB = F - F +
B B

(2)

1

F =
0

d d (cos ) d (cos )

(3)

0

B =
-1

d d (cos ) d (cos )

(4)

Where - is the angle between Å- and quark momentum in dimuon center of mass frame.
Study of the Drell-Yan process with CMS. 15/23

I. Gorbunov Ilya.Gorbunov@cern.ch


Application of AFB
Measurement of the AFB can provide: Test of the SM in the new energy region Provide at the Z-pole a precise measurement of sin2 W Deviations from the SM predictions for AFB may indicate the existence of: A new neutral gauge boson Quark-lepton compositeness Existence of supersymmetric particles Extra dimensions, etc.
In case of BSM physics A
FB

can help to determine it's nature
Study of the Drell-Yan process with CMS. 16/23

I. Gorbunov Ilya.Gorbunov@cern.ch


Reference System

On pp colliders quark and antiquark directions are unknown Dimuon boost direction is assumed to be the quark direction

The Collins-Soper frame where the angle is defined to be the angle between the lepton momentum and a z-axis that bisects the angle between q and q directions is used. This frame ? reduces the uncertainties due to the transverse momentum of quarks. d = A(1+cos2 )+B cos d cos (5)

I. Gorbunov Ilya.Gorbunov@cern.ch

Study of the Drell-Yan process with CMS.

17/23


Background and Uncertainties
Main sources of background: For low masses
Z QCD dijets

t ? for high masses t AFB measurement lead to a large systematic uncertainty and thus requires correction on the following effects: Finite detector resolution and alignment QED FSR Acceptance Unknown quark antiquark direction at the LHC

I. Gorbunov Ilya.Gorbunov@cern.ch

Study of the Drell-Yan process with CMS.

18/23


Selection Cuts for Muon Candidates
Kinematics: Oppositely charged global and tracker muons | | < 2.4 and pT > 20 GeV Quality requirements: > 10 tracker hits, > 1 pixel hits, > 1 muon hits > 2 muon stations 2 < 10 for the global fit Small impact parameter d0 < 0.2 Remove back-to-back dimuons > 2.5 mrad Isolation: Tracker+HCAL isolation ( pT (tracks ) + ET (had ))/pT (Å) < 0.15
I. Gorbunov Ilya.Gorbunov@cern.ch Study of the Drell-Yan process with CMS. 19/23


Selection Cuts for Electron Candidates
Kinematics: Oppositely charged electrons | | < 1.444 or 1.566 < | | < 2.5 HLT ECAL L1-trigger requiring an ECAL cluster with minimum ET between 10 to 17 GeV Quality requirements: Minimum supercluster E

T

of 20 GeV

No missing Tracker hits before the first one Reject when a conversion partner track close to the electron Using shower shape variables Isolation: Isolation using the Tracker and calorimeters
I. Gorbunov Ilya.Gorbunov@cern.ch Study of the Drell-Yan process with CMS. 20/23


CMS Results with 5 fb

-1

arXiv:1207.3973 ; CMS-EWK-11-004 ; CERN-PH-EP-2012-187. - 2012. - 29 p.
I. Gorbunov Ilya.Gorbunov@cern.ch Study of the Drell-Yan process with CMS. 21/23


CMS Results (sin2 W )
d pp l + l - X (Y , s , cos ) X even 2 2 odd 2 [qq (s , cos , sin W )+Dq q (s , Y )çq q (s , cos , sin W ]Fq q (s , Y ) ^ ^? ? ? dYdsd cos q =u ,d ,s ,c ,b (6)

sin2

W

= 0.2287 Á 0.0020(stat .) Á 0.0025(syst .)
2

(7)

Systematic uncertainties in the measurement of sin W : Source Correction Uncertaintie PDF Á0.0013 FSR Á0.0011 LO model (EWK) Á0.0002 +0.0012 Á0.0012 LO model (QCD) Resolution/alignment +0.0007 Á0.0013 Acceptance and Efficiency Á0.0003 Background Á0.0001 Total +0.0019 Á0.0025 Phys. Rev. D 84, 112002 (2011)
I. Gorbunov Ilya.Gorbunov@cern.ch Study of the Drell-Yan process with CMS. 22/23


Conclusion

Drell-Yan process is a good probe for new physics sin2 W , AFB and DY cross section measurements are consistent with the Standard Model predictions within uncertainties

I. Gorbunov Ilya.Gorbunov@cern.ch

Study of the Drell-Yan process with CMS.

23/23