Precision Forward Measurements at LHCb with Vector Bosons · Introduction Trigger JINST 8 (2013) P04022 • movable L0 thresholds and software HLT • low p T leptons/photons and

Precision Forward Measurements at LHCb withVector Bosons

Philip Iltenon behalf of the LHCb Collaboration

Massachusetts Institute of Technology

Radcor-Loopfest

Ilten Measurements with LHCb June 18, 2015 1 / 37

Introduction

Detector JINST 3 (2008) S08005

VELO

RICH1

TT

magnet

OT

IT

T1

T2

T3

RICH2

M1

M2 M3 M4 M5

HCAL

ECALmuon system5 m

5 m 15 mz-axis →

y-ax

is→

SPD/PRS

• fully instrumented between 2 < η < 5• performance documented in Int. J. Mod. Phys. A 30 (2015) 07• momentum resolution between 0.4% at 5 GeV to 1% at 200 GeV• impact parameter resolution of 15 + 29/pT µm• secondary vertex precision of 0.01− 0.05(0.1− 0.3) mm in xy(z)


http://dx.doi.org/10.1088/1748-0221/3/08/S08005

http://arxiv.org/abs/1412.6352

Introduction

Trigger JINST 8 (2013) P04022

• movable L0 thresholds andsoftware HLT

• low pT leptons/photons andtracks (IP > 0.1 mm)

L0

µ: pT > 1.5 GeV

340 kHz

µµ:√

p1Tp2

T > 1.3 GeV

75 kHz

h: ET > 3.5 GeV

405 kHz

e: ET > 2.5 GeV

160 kHz

γ: ET > 2.5 GeV

80 kHz

µ: pT > 4.8(1) GeV

0.7(5) kHz

µµ: m > 2.7(1)GeV

1.2(1.3) kHz

track: pT > 1.7 GeV

33 kHz

e: pT > 10 GeV

. . .

µ: pT > 10(4.8) GeV

µµ: m > 4.8(3) GeV

displaced vertex

inclusive topological

beauty BBDT

inclusive and

exclusive charm

. . .

15 MHz 5 kHz

HLT1 HLT2

1 MHz 50 kHz



Introduction

Datasets JINST 9 (2014) 12,P12005

• 1 fb−1 pp collisions at√

s = 7 TeV(2011)

• 2 fb−1 pp collisions at√

s = 8 TeV(2012)

• 1.1 nb−1 pPb collisions at√s = 5 TeV (2013)

• 0.5 nb−1 Pbp collisions at√s = 5 TeV (2013)

• excellent luminosity uncertainty• 1.71% for 7 TeV dataset• 1.16% for 8 TeV dataset

date [day/month]28/02 09/04 19/05 29/06 08/08 18/09 28/10

L[ fb−

1]

0

1

2

3

4

5

6LHCbATLASCMS

√s = 7 TeV

(2011)

date [day/month]28/02 18/04 05/06 23/07 09/09 27/10 14/12

L[ fb−

1]

0

5

10

15

20

25

30LHCbATLASCMS

√s = 8 TeV

(2012)




Inclusive W/Z Measurements

Inclusive W /Z Measurements



Inclusive W arXiv:1505.07024

• 1.0 fb−1 7 TeV dataset• W [µν] final state• signal fiducial definition

• 2.0 < η(µ) < 4.5• pT(µ) > 20 GeV

• purity of ≈ 77% IP [mm]0 0.5 1 1.5

Eve

nts

per

0.02

mm

10

210

310

410

510

610LHCb

DataFit

(data)WPseudo- (simulation)ντ →W

(simulation)µ X→ c+cbb

JHEP 1404 (2014) 091

]c [GeV/T

p

cE

vent

s pe

r 1

GeV

/

10000

20000

30000LHCb +µ -µ < 4.5η2.0 <

Data νµ → πK/

Fit Electroweak

νµ →W Heavy flavour

]c [GeV/T

p

Pull

-5

0

5

20 30 40 50 60 70 20 30 40 50 60 70

JHEP 1404 (2014) 091






Inclusive W : Systematics arXiv:1505.07024

source δσ(W +) [%] δσ(W−) [%] δRW [%]

template shape 0.28 0.39 0.59template normalization 0.10 0.10 0.06reconstruction efficiency 0.60 0.56 0.21selection efficiency 0.33 0.32 0.18acceptance and FSR 0.18 0.12 0.21systematic 0.76 0.77 0.69statistical 0.23 0.28 0.39luminosity 1.71 1.71




Inclusive W : Integrated σ arXiv:1505.07024

• compared with fixed order FEWZ using MSTW08, NNPDF 2.3,CT10, ABM12, HERA15, JR09

σ(W +) = 878.0± 2.1± 6.7 ± 15.0 pbσ(W−) = 689.5± 2.0± 5.3± 11.8 pbRW = 1.274± 0.005± 0.009

=575TeVsLHCb:5

statData

totData

MSTW+8

NNPDF3+

CT-+

ABM-2

HERA-5

JR+9

>52+5GeV]cµ

Tp

<54[5µη2[+5<52<5-2+5GeV]cµµZ:56+5<5M

8++ 82+ 84+ 86+ 88+ 9++ 92+ 94+[pb]νZµ→ZWσ

64+ 66+ 68+ 7++ 72+ 74+[pb]

ν6µ→6Wσ

-[2 -[25 -[3 -[35 ν6µ→6Wσ

νZµ→ZWσ

[pb]νRµ→RWσ

8rc 9cc 9rc

[pb]

ν>µ

→>

Wσ

6rc

7cc

7rc

8cc=M7MTeVsLHCbJM

Data

syst⊕statMData

lumi⊕beamM⊕systM⊕statMDataMSTWc8NNPDF.cCT<cABM<4HERA<rJRc9

>M4cMGeV/cµ

Tp

<M%Grµη4GcM<M

68G.3MCLMellipseMarea




Inclusive W : Differential σ arXiv:1505.07024

µη

[pb

]µ η

/d νµ →

W

σd

200

400

600

800 = 7 TeVsLHCb,

)+ (WstatData MSTW08

)+ (WtotData NNPDF30

)- (WstatData CT10

)- (WtotData ABM12

HERA15

JR09

> 20 GeV/cµT

p

µη2 2.5 3 3.5 4 4.5T

heor

y/D

ata

µη

0.91

1.1

µη

0.91

1.1

µηW

R

0.5

1

1.5

2 = 7 TeVsLHCb,

statData MSTW08

totData NNPDF30

CT10

ABM12

HERA15

JR09

> 20 GeV/cµT

p

µη2 2.5 3 3.5 4 4.5T

heor

y/D

ata

0.81

1.2

η

µA

0.4−

0.2−

0

0.2

0.4 = 7 TeVsLHCb,

statData MSTW08

totData NNPDF30

CT10

ABM12

HERA15

JR09

> 20 GeV/cT

p

η2 2.5 3 3.5 4 4.5T

heor

y-D

ata

0.05−0

0.05




Inclusive W : Comparison arXiv:1505.07024

µη0 1 2 3 4

[pb

]µ η

/d νµ →

W

σd

0

200

400

600

= 7 TeVsν+µ → +LHCb (2011 extrapolated) W

ν-µ → -LHCb (2011 extrapolated) Wν+µ → +ATLAS (2010) W

ν-µ → -ATLAS (2010) W

> 20 GeV/cµT

p2 > 40 GeV/cTM

> 25 GeVmissE

lη0 1 2 3 4

lA

0.6−

0.4−

0.2−

0

0.2

0.4

0.6

= 7 TeVsνµ →LHCb (2011 extrapolated) W

ν e→ and W νµ →ATLAS (2010) W

> 20 GeV/clT

p2 > 40 GeV/cTM

> 25 GeVmissE

µη0 1 2 3 4

µA

0.6−

0.4−

0.2−

0

0.2

0.4

0.6

= 7 TeVsνµ →LHCb (2011 extrapolated) W

νµ →CMS (2011) W

> 20 GeV/cµT

p




Inclusive Z [µµ] arXiv:1505.07024

• 1.0 fb−1 7 TeV dataset• signal fiducial definition

• 2.0 < η(µ) < 4.5, pT(µ) > 20 GeV• 60 < M (µµ) < 120 GeV

• purity of ≈ 99.3%• beam energy

uncertainty of 1.3%

source δσ(Z) [%] δRWZ [%] δRW+Z[%] δRW−Z

[%]

trigger efficiency 0.07 0.15 0.16 0.13ID efficiency 0.23 0.12 0.12 0.12tracking efficiency 0.53 0.24 0.23 0.26final state radiation 0.11 0.16 0.21 0.17purity 0.22 0.41 0.49 0.55GEC efficiency 0.26 0.27 0.28 0.29systematic 0.68 0.60 0.67 0.72statistical 0.39 0.45 0.48 0.50luminosity 1.72




Inclusive Z [µµ]: Integrated σ arXiv:1505.07024

• compared with fixed orderFEWZ using MSTW08,NNPDF 2.3, CT10, ABM12,HERA15, JR09

=575TeVsLHCb:5

statData

totData

MSTW[8

NNPDF3[

CT][

ABM]2

HERA]5

JR[9

>52[5GeV+cµ

Tp

<54-5µη2-[5<52<5]2[5GeV+cµµZ:56[5<5M

][-8 ]] ]]-2 ]]-4 ]]-6 ]]-8 ]2 ]2-2 6µZµ→Z5σνZµ→ZW

σ

8-6 8-8 9 9-2 9-4 9-6 6µZµ→Z5σν6µ→6W

σ

]9-5 2[ 2[-5 2] 2]-5 22 6µZµ→Z5σνµ→W5σ

7[ 72 74 76 78 8[ 82[pb]6µZµ→Zσ

[pb]>µRµ→Ziσ

rc r6 8c

[pb]

νRµ

→R

Wσ

86c

9cc

96c

<ccc

<c6c=iriTeVsLHCbJi

Data

syst⊕statiData

lumi⊕beami⊕systi⊕statiDataMSTWc8NNPDF.cCT<cABM<4HERA<6JRc9

>i4ciGeV/cµ

Tp

<i:G6µη4Gci<i

4<i<4ciGeV/cµµZ:i%ci<iM

%8G.FiCLiellipseiarea

[pb]9µRµ→Zσ

r/ r: 8/

[pb]

ν9µ

→9

Wσ

%:/

r//

r:/

8//=MrMTeVsLHCbJ

Data

syst⊕statData

lumi⊕beam⊕syst⊕statDataMSTW/8NNPDF4/CTc/ABMc<HERAc:JR/9

>M</MGeVGcµ

Tp

<M.>:µη<>/M<

<<Mc</MGeVGcµµZ:M%/M<MM

%8>43MCLMellipseMarea




Inclusive Z [µµ]: Differential σ arXiv:1505.07024

Zy

2 2.5 3 3.5 4 4.5

Z/d

yσd

0

10

20

30

40

50

60

70

80

totData

statData

MSTW08

NNPDF30

CT10

ABM12

HERAPDF1.5

JR09

= 7 TeVsLHCb,

Zy

2 2.5 3 3.5 4 4.5

Zdy

σd σ1

0

0.2

0.4

0.6

0.8

1totData

statData

RESBOS

POWHEG+HERWIG

= 7 TeVsLHCb,

[GeV/c]T,Z

p1 10 210

]-1

[(G

eV/c

)T,

Zdp

σdσ1

0

0.02

0.04

0.06

0.08

0.1totData

statData

RESBOS

POWHEG+HERWIG

= 7 TeVsLHCb,

[GeV/c]T,Z

p1 10 210

]-1

[(G

eV/c

)T,

Zdp

σdσ1

0

0.02

0.04

0.06

0.08

0.1totData

statData

HERWIRI

= 0 GeV/c>2T<kHW:

= 2.2 GeV/c>2T<kHW:

= 7 TeVsLHCb,




Inclusive Z [ee] JHEP 1505 (2015) 109

• 2.0 fb−1 8 TeV dataset (7 TeV JHEP 1302 (2013) 106)• signal fiducial definition same as inclusive Z [µµ]• purity of ≈ 93%

source δσ(Z) [%]

track efficiency 1.0kinematic efficiency 0.6ID efficiency 0.7global event cut 0.6trigger efficiency 0.1background 0.4systematic 1.6statistical 0.4luminosity 1.2

• comparison with fixed orderFEWZ

BC[pb]-e+e→Z→Appσ70 75 80 85 90 95

-e+e→8CTeVCZC

DataCAstat.B

DataCAtot.BNNLO/MSTW08

NNLO/CTEQ10

NNLO/NNPDF23

NNLO/NNPDF30

NNLO/ABM12

LHCb





Inclusive Z [ee]: Differential σ JHEP 1505 (2015) 109

Z

y 2 2.5 3 3.5 4

[pb

]Zy

/dσ d

0

10

20

30

40

50

60

70

80

90

-e+ e→8 TeV Z

Data (stat.)

Data (tot.)

NNLO/MSTW08

NNLO/CT10

NNLO/NNPDF23

NNLO/NNPDF30

NNLO/ABM12

LHCb

Z

y 2 2.5 3 3.5 4

Zy/dσ

)dσ (

1/

0

0.1

0.2

0.3

0.40.5

0.6

0.7

0.8

0.91

-e+ e→8 TeV Z

Data (stat.)

Data (tot.)

Pythia8.1

Resbos

Powheg

LHCb

* φ -210 -110 1

*φ/dσ

)dσ (

1/

-310

-210

-110

1

10

-e+ e→8 TeV Z

Data (stat.)Data (tot.)Pythia8.1ResbosPowheg

LHCb

* φ -210 -110 1

Pre

dict

ion/

data

0

0.2

0.4

0.6

0.81

1.2

1.4

1.6

1.82

-e+ e→8 TeV Z Data (stat.)Data (tot.)Pythia8.1ResbosPowheg

LHCb



Z + X Measurements

Z + X Measurements


Z + X Measurements

Z + j JHEP 1401 (2014) 033

• 1.0 fb−1 7 TeV dataset• Z [µµ] + j final state• signal fiducial definition

• same as inclusive Z [µµ]• ∆R(µ, j) > 0.4

• jet definition• anti-kT with R = 0.5• pT(j) > 10, 20 GeV• 2.0 < η(j) < 4.5

• purity of ≈ 99.6%• Z + b analysis in JHEP 1412

(2014) 079

ZT

p / jetT

p0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0

Frac

tion

of e

vent

s

0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

Data

Simulation

LHCb

source δσ [%]

unfolding 1.5Z reconstruction 3.5jet scale, resolution, rec. 7.8final state radiation 0.2

systematic 8.6statistical 1.6luminosity 3.5





Z + X Measurements

Z + j : Integrated σ JHEP 1401 (2014) 033

• comparison with fixed order FEWZ and showered POWHEG• MSTW08, CTEQ10, and NNPDF 2.3 PDF sets used

min pT(j) [GeV] σ(Z + j)/σ(Z) [pb] σ(Z + j) [pb]

10 0.209± 0.002± 0.015 16.0± 0.2± 1.2± 0.620 0.083± 0.001± 0.007 6.3± 0.1± 0.5± 0.2

(Z)

σ(Z+

jet)

σ

0.07

0.08

0.09

0.10

0.11

0.12

0.13

0.14 Data (stat.)Data (tot.)

)sα(OPOWHEG + PYTHIA, MSTW08, )2

sα(OPOWHEG + PYTHIA, MSTW08, )2

sα(OPOWHEG + PYTHIA, CTEQ10, )2

sα(OPOWHEG + PYTHIA, NNPDF 2.3, )2

sα(OFEWZ, MSTW08,

= 7 TeV Datas

> 20 GeVjet

Tp

LHCb

(Z)

σ(Z+

jet)

σ

0.16

0.18

0.20

0.22

0.24

0.26

0.28

0.30

0.32 Data (stat.)Data (tot.)

)sα(OPOWHEG + PYTHIA, MSTW08, )2

sα(OPOWHEG + PYTHIA, MSTW08, )2

sα(OPOWHEG + PYTHIA, CTEQ10, )2

sα(OPOWHEG + PYTHIA, NNPDF 2.3, )2

sα(OFEWZ, MSTW08,

LHCb

= 7 TeV Datas

> 10 GeVjet

Tp



Z + X Measurements

Z + j : Differential σ JHEP 1401 (2014) 033

[GeV]ZT

p0 20 40 60 80 100

[1

/GeV

]Z T

pdσd σ1

-210

-110

Data (stat.)Data (tot.)

)sα(OMSTW08, )2

sα(OMSTW08, )2

sα(OCTEQ10, )2

sα(ONNPDF 2.3,

POWHEG + PYTHIA: = 7 TeV Datas

> 20 GeVjetT

p

LHCb

φ∆0 1 2 3

φ∆dσd σ1

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

Data (stat.)Data (tot.)

)sα(OMSTW08, )2

sα(OMSTW08, )2

sα(OCTEQ10, )2

sα(ONNPDF 2.3,

POWHEG + PYTHIA:

= 7 TeV Datas

> 20 GeVjet

Tp

LHCb

[GeV]jetT

p20 40 60 80 100 120 140

[1

/GeV

]je

tT

pdσd

σ1

-410

-310

-210

-110Data (stat.)Data (tot.)

)sα(OMSTW08, )2

sα(OMSTW08, )2

sα(OCTEQ10, )2

sα(ONNPDF 2.3,

POWHEG + PYTHIA:

= 7 TeV Datas

> 10 GeVjet

Tp

LHCb

y∆-2 -1 0 1 2

y∆dσd

σ1

0.0

0.2

0.4

0.6

0.8

1.0

1.2Data (stat.)Data (tot.)

)sα(OMSTW08, )2

sα(OMSTW08, )2

sα(OCTEQ10, )2

sα(ONNPDF 2.3,

POWHEG + PYTHIA: = 7 TeV Datas

> 20 GeVjet

Tp

LHCb



Z + X Measurements

Z + D JHEP 1404 (2014) 091

• 1.0 fb−1 7 TeV dataset• Z [µµ] + c-hadron final state

• D0[K−π+], D+[K−π+π+]• D+

s [π+φ[K+K−]],Λ+

c [pK−π+]• signal fiducial definition

• same as inclusive Z [µµ]• 3.2 < p(K , π) < 100 GeV• pT(K , π) > 250 MeV• 2 < y(D)• 2 < pT(D) < 12 GeV

• 7 D0 and 4 D+ observed• purity of ≈ 95.6%

• feed-down from simulation• combinatorial from 2D mass• pile-up from χ2 vertex fit

[GeV]−µ+µm60 70 80 90 100 110 120

[G

eV]

+ π−K

m

1.83

1.84

1.85

1.86

1.87

1.88

1.89

1.9

1.91

-1010

-910

-810

-710

-610

-510

-410

-310LHCb

0Z + D

source δσ(D0) [%] δσ(D+) [%]

efficiency 6.8 5.0pile-up 0.6 0.6feed-down 3.9 1.1BD 1.3 2.1

systematic 8.0 5.6statistical 44.8 52.3luminosity 3.5 3.5



Z + X Measurements

Z + D: Cross-section JHEP 1404 (2014) 091

• single parton scattering (SPS)from fixed order MCFM usingMSTW08

• corrected for fragmentation• double parton scattering (DPS)

using pocket formula

σ(AB) = σ(A)σ(B)/σeff

• Z and D cross-sections fromLHCb

σ(Z + D0) = 2.50± 1.12± 0.22 pb

σ(Z + D+) = 0.44± 0.23± 0.03 pb 0D+D s

+D c+Λ

cros

smse

ctio

nm[fb

]210

310

410

=7mTeVsLHCbmdatam

SPSmmassive

SPSmmassless

DPS



W + j Measurements

W + j Measurements


W + j Measurements

Q-tagging arXiv:1504.07670

• build 2-body SVs• n-body SVs from linking 2-body SVs with

shared tracks• require vertex flight direction within jet,

∆R(SV, j) < 0.5• two BDTs

• BDT(bc|udsg): udsg-jet from b, c-jet• BDT(b|c): b-jet from c-jet

SV

jet

PV

variable separation variable separationM (SV) udsgc b Mcor(SV) udsgb cmin(FDT(SV)) udsg cb pT(SV)/pT(j) udsg cb∆R(SV, j) udsg cb N (trk) udsgc bN (trk ∈ j) udsgc b |Q(SV)| udsgb clog(χ2

FD(SV)) all log(χ2IP(SV)) all



W + j Measurements

Q-tagging: Flavor arXiv:1504.07670

• fit 2-dimensional BDT(bc|udsg) versus BDT(b|c) distributions

)udsg|bcBDT(-1 -0.5 0 0.5 1

)c|bB

DT

(

-1

-0.5

0

0.5

1

LHCb simulation

-jetsudsg

)udsg|bcBDT(-1 -0.5 0 0.5 1

)c|bB

DT

(

-1

-0.5

0

0.5

1

LHCb simulation

-jetsc

)udsg|bcBDT(-1 -0.5 0 0.5 1

)c|bB

DT

(

-1

-0.5

0

0.5

1

LHCb simulation

-jetsb

)udsg|bcBDT(-1 -0.5 0 0.5 1

cand

idat

es

0

2000

4000

6000

8000 LHCbdatabc

udsg

)c|bBDT(-1 -0.5 0 0.5 1

cand

idat

es

0

2000

4000

6000 LHCbdatabc

udsg



W + j Measurements

Q-tagging: Efficiency arXiv:1504.07670

• determine efficiency with: Nx(SV)Nx(χ2

IP) , x ∈ udsg, c, b

c-enhanced (D + j) b-enhanced (B + j)

χ2IP of hardest-pT

track (large initialudsg-background)

)IP2χlog(

-5 0 5 10 15

cand

idat

es

0

50000

100000

150000 LHCbdatabc

udsg

+jetD

)IP2χlog(

-5 0 5 10 15

cand

idat

es

0

10000

20000

LHCbdatabc

udsg

+jetB

χ2IP of hardest-pT

muon (only O(10%)of jets)

)IP2χmuon log(

-5 0 5 10 15

cand

idat

es

0

500

1000

1500

2000

LHCbdatabc

udsg

+jetD

)IP2χmuon log(

-5 0 5 10 15

cand

idat

es

0

1000

2000

LHCbdatabc

udsg

+jetB



W + j Measurements

Q-tagging: Results arXiv:1504.07670

light-parton mistag probability0.001 0.002 0.003 0.004 0.005

(b,c

)-je

t tag

eff

icie

ncy

0

0.2

0.4

0.6

0.8

1

-jetb-jetc

LHCb simulation

(jet) < 4.2η2.2 <

(jet) < 100 GeVT

20 < p

(jet) [GeV]T

p20 40 60 80 100

SV-t

ag e

ffic

ienc

y0

0.2

0.4

0.6

0.8

1LHCb

-jetb

-jetc



W + j Measurements

Q-tagging: Systematics arXiv:1504.07670

source b-jets c-jetsBDT templates∗ ≈ 2% ≈ 2%udsg-jet large IP component∗ ≈ 5% ≈ 10− 30%IP resolution − −hadron-as-muon (hardest-µ only) 5% 20%out-of-jet (b, c)-hadron decay − −gluon splitting 1% 1%pile up − −

systematic (combined fit) ≈ 10% ≈ 10%∗dependent on jet type and pT



W + j Measurements

W + b, c arXiv:1505.04051

• 7 TeV and 8TeV datasets• fiducial definition:

• same as inclusive W• pT(j) > 20 GeV• 2.2 < η(j) < 4.2• ∆R(µ, j) > 0.5• pT(µ+ j) > 20 GeV

• W + j content from isolation fit• BDT(bc|udsg) and BDT(b|c) fit• W + b-jet: top extrapolated

from side-band• W + c-jet: Z [ττ ] from

pT(SV)/pT(j) fit

0.5 0.6 0.7 0.8 0.9 1

Can

dida

tes/

0.05

20000

40000 Data

W

Z

Jets

= 8 TeVs, +µ

) µj(T

p)/µ(T

p0.5 0.6 0.7 0.8 0.9 1

cand

idat

es

20000

40000 = 8 TeVs, −µ LHCb



W + j Measurements

W + b, c: Systematics (5) arXiv:1505.04051

source δσ(Wb)σ(Wj)

[%] δσ(Wc)σ(Wj)

[%] δσ(Wj)σ(Zj)

[%] δA(Wb) δA(Wc)

(b, c)-tag efficiency 10 10 − −isolation templates 10 5 4 0.08 0.03top 13 − − 0.02SV-tag BDT templates 5 5 0.02 0.02Z [ττ ] − 3 − − −jet reconstruction 2 2 − − −jet energy 2 2 1 0.02 0.02trigger and selection 1 1 2 − −W [τν] − − 1 − −other electroweak − − − − −

systematic 20 13 5 0.09 0.04statistical (7 TeV) 20 8 2 0.20 0.08statistical (8 TeV) 10 5 1 0.13 0.05



W + j Measurements

W + b, c: Ratios arXiv:1505.04051 1

00×

(Wj)

σ(W

x)/

σ

0

1

2

3

4

5

6

7 = 7 TeV LHCb datas = 8 TeV LHCb datas

(Zj)

σ(W

j)/σ

5

6

7

8

9

10

11

12 = 7 TeV LHCb datas = 8 TeV LHCb datas

A(W

x)

-0.2

0

0.2

0.4

0.6

0.8 = 7 TeV LHCb datas = 8 TeV LHCb datas points data (total, stat)fills MCFM NLO theory

CT10 (scale + PDF)green W + c-jetred W + b-jetblue W + + jmagenta W− + j



W + j Measurements

Top arXiv:1506.00903

• tightened fiducial region• pT(µ) > 25 GeV reduces di-jet background• 50 < pT(b) < 100 GeV reduces W + b

• similar analysis strategy to W + b, c ratios• fit pT(µ+ b) and A distributions to determine significance• use excess from W + b prediction to calculate cross-section

)µ

j(T

p)/µ(T

p0.5 0.6 0.7 0.8 0.9 1

Can

dida

tes/

0.05

5000

10000

Data

W

Z

Jets

LHCb+jetµ

)µ

j(T

p)/µ(T

p0.5 0.6 0.7 0.8 0.9 1

Can

dida

tes/

0.1

100

200

300

Data

W

Z

Jets

LHCb-tag+bµ



W + j Measurements

Top: Background arXiv:1506.00903

) [GeV]j+µ(T

p

+je

t)W(

N

0

2000

4000

6000

8000 LHCb

Data

SM

20 45 70 95 ∞) [GeV]j+µ(

Tp

Cha

rge

Asy

mm

etry

-0.4

-0.2

0

0.2

0.4

20 45 70 95 ∞

LHCb

Data

SM

• constrain W + b backgroundusing W + j from data andW + b/W + j from theory

• theory and experimentaluncertainties partiallycancel

• validate against W + c ) [GeV]c+µ(T

p

)c+

W(N

0

50

100

150

200

Data

SM

LHCb

20 45 70 95 ∞



W + j Measurements

Top: Significance arXiv:1506.00903

• profile likelihood used tocompare W + b hypothesis withW + b + top

• uncertainties treated asGaussian nuisanceparameters

• 5.4σ significance observed

source δσ [%]

GEC 2pT(µ)/pT(jµ) templates 5–10jet reconstruction 2SV-tag BDT templates 5b-tag efficiency 10

trigger & µ selection 2jet energy 5W [τ [µνν]ν] 1

luminosity 1–2

) [GeV]b+µ(T

p

)W

+b

(N

0

100

200

Data+topWb

Wb

LHCb

20 45 70 95 ∞) [GeV]b+µ(

Tp

Cha

rge

Asy

mm

etry

-0.4

-0.2

0

0.2

0.4

Data

+topWb

Wb

LHCb

20 45 70 95 ∞



W + j Measurements

Top: Cross-section arXiv:1506.00903

• cross-section determined from subtracting W + b background fromdata

) [fb

]t

+ t

+

t(tσ

100

150

200

250

300

350

400

= 7 TeV LHCb datas = 8 TeV LHCb datas

σ(tt̄ + t + t̄)points data (total, stat)fills MCFM NLO theory

CT10 (scale + PDF)



Conclusions

Conclusions


Conclusions

Run 2 and Beyond

• projected luminosity

LHC era HL-LHC era

Run 1(a) Run 1(b) Run 2 Run 3 Run 4 Run 52011 2012 2015 - 2018 2020 - 2022 2025 - 2028 2030 - ?

1 fb−1 2 fb−1 5 fb−1 15 fb−1 25 fb−1 50 fb−1

• LHCb upgrade during LS 2, see LHCb-PUB-2014-040• replacement of RICH and tracking• full software trigger, see LHCb-TDR-016

• current hardware readout at 1 MHz, upgrade at 40 MHz

• significantly more top statistics in the future• double vector boson measurements possible• Higgs in the not-so-near future?


https://cds.cern.ch/record/1748643

https://cds.cern.ch/record/1701361

Conclusions

Final Thoughts

• LHCb has a diverse physics program, far beyond original design• what would others like to see from LHCb?• some (probably unreasonable) technical requests

• keep in mind fiducial definition for LHCb• prefer tools that don’t require file interfaces (i.e. LHEF)

• looking forward to Run 2 data

Thank you!


Documents

Precision Forward Measurements at LHCb with Vector Bosons · Introduction Trigger JINST 8 (2013) P04022 • movable L0 thresholds and software HLT • low p T leptons/photons and