Heavy Flavor and Jet Production at LHCb Mike Williams on behalf of - - PowerPoint PPT Presentation

SLIDE 1

Heavy Flavor and Jet Production at LHCb

Mike Williams

• n behalf of the LHCb Collaboration

Department of Physics & Laboratory for Nuclear Science Massachusetts Institute of Technology January 12, 2016

SLIDE 2

The Large Hadron Collider

LHCb overview

• pen beauty & charm

jets (V+j,b-jets,c-jets,...) quarkonia fixed-target running

Outline {

SLIDE 3

VELO Magnet MUON Tracking CALO RICH stuff

3

LHCb Detector

] c

• 1

[GeV

T

p 1/ 0.5 1 1.5 2 2.5 3 m] µ resolution [

x

IP 10 20 30 40 50 60 70 80 90 100 2012 data Simulation

LHCb

Momentum (GeV/c)

20 40 60 80 100

Efficiency

0.2 0.4 0.6 0.8 1 1.2 1.4

) > 0

• LogL(K -
• ) > 5
• LogL(K -
• K
• K

K

• LHCb Data
• JINST 3 (2008) S08005

Int.J.Mod.Phys. A 30(2015) 1530022

) µ → π (

DLL

℘

0.005 0.01

DLL

ε

0.2 0.4 0.6 0.8 1 DLL muDLL LHCb (a)

LHCb is a forward Spectrometer (2 < η < 5)

SLIDE 4

4

Plan to move to a triggerless-readout system in Run 3!

LHCb Trigger

40 MHz bunch crossing rate

450 kHz h± 400 kHz µ/µµ 150 kHz e/γ

L0 Hardware Trigger : 1 MHz readout, high ET/PT signatures

Software High Level Trigger

12.5 kHz Rate to storage

Partial event reconstruction, select displaced tracks/vertices and dimuons Buffer events to disk, perform online detector calibration and alignment Full offline-like event selection, mixture

• f inclusive and exclusive triggers

LHCb 2015 Trigger Diagram

Precision measurements benefit greatly from using the final (best) reconstruction in the online event selection -- need real- time calibration!

all tracks pT > 0.5 GeV (no IP requirements) same calibration constants used online &

• ffline

full reconstruction, offline-like particle ID, track quality, etc.

Heavy use of machine learning algorithms throughout the Run 1 and Run 2 trigger. V.Gligorov, MW, JINST 8 (2012) P02013.

JINST 8 (2013) P04022

SLIDE 5

5

Complimentary kinematical coverage to CMS & ATLAS.

LHCb Detector

Cherenkov drift tube pixel silicon strip ECAL HCAL muon

LHCb CMS

SLIDE 6

6

LHCb Physics

Core physics program involves searching for BSM physics in the decays of heavy-flavor hadrons -- but their production is also of great interest!

x

6 −

10

5 −

10

4 −

10

3 −

10

2 −

10

1 −

10 1

]

2

[GeV

2

Q

1 10

2

10

3

10

4

10

5

10

6

10

7

10

LHCb ATLAS/CMS Tevatron HERA fixed target

LHCb probes unique regions of (x,Q) so there are many measurements we can (potentially) make that are sensitive to (largely unknown) PDFs*.

*PDFs means “parton distribution functions” throughout this talk.

Q2(x) = e±2yx2s

SLIDE 7

7

Open Charm

m(K−π+) [MeV/c2]

1800 1850 1900

Candidates / (1 MeV/c2)

50 100 150 ×103 D0 data Fit

• Sig. + Sec.
• Comb. bkg.

LHCb √s = 13TeV

2 4 6 8 10 12 14 pT [GeV/c] 10−9 10−8 10−7 10−6 10−5 10−4 10−3 10−2 10−1 100 101 102 103 (d2σ)/(dydpT)·10−m [µb/(GeVc−1)] 2.0 < y < 2.5, m = 0 2.5 < y < 3.0, m =2 3.0 < y < 3.5, m =4 3.5 < y < 4.0, m =6 4.0 < y < 4.5, m =8

LHCb D0

√s = 13 TeV POWHEG+NNPDF3.0L FONLL GMVFNS )]

LHCb-PAPER-2015-041

<x1> ~ 0.05, <x2> ~ 2e-5 Results also published for D+, Ds, D* at both 7 and 13 TeV. σ(cc)[13TeV] shown @ EPS (2015) within a week of recording the data; it was measured using online-reconstructed data. Excellent probe of the small-x gluon PDF.

POWHEG+NNPDF [1506.08025], FONLL [1507.06197], GMVFNS [1202.0439]

SLIDE 8

[ps]

z

t

• 10
• 8
• 6
• 4
• 2

2 4 6 8 10

Candidates per 0.2 ps

1 10

2

10

3

10

4

10

5

10

• 1

=3.05 pb

int

L = 13 TeV, s LHCb c < 3 GeV/

T

p 2 < < 3.5 y 3 <

Data Total fit b

• from-

ψ J/ ψ Prompt J/ Wrong PV Background

8

The pseudo-lifetime distribution of J/ψ’s is fitted to determine both the prompt and “from b” content. LHCb has also measured production of many open- beauty meson and baryon species separately.

Open Beauty

] c ) [GeV/ ψ J/ (

T

p

5 10

)] c ) [nb/(GeV/

T

p d y /(d σ

2

d

1 10

2

10

• 1

=3.05 pb

int

L = 13 TeV, s LHCb <2.5 y 2.0< <3.0 y 2.5< <3.5 y 3.0< <4.0 y 3.5< <4.5 y 4.0<

σ(bb)[13TeV] also shown at EPS, and previously measured at lower energies.

LHCb-PAPER-2015-037: JHEP 10 (2015) 172

tz =

• zJ/ψ − zPV
• × MJ/ψ

pz ,

See http://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/Summary_all.html for all LHCb publications.

SLIDE 9

9

See also Gauld et al [1511.06346] for updated prompt atmospheric neutrino flux predictions for IceCube constrained by LHCb prompt-charm data.

Example Impact

x

6 −

10

5 −

10

4 −

10

3 −

10

2 −

10

1 −

10

)

2

= 4 GeV

2

g ( x, Q 2 4 6 8 10 12 14 16

data

+-

,D no LHCb D data (wgt)

+-

,D with LHCb D data (unw)

+-

,D with LHCb D

=0.118

s

α NNPDF3.0 NLO

x

6 −

10

5 −

10

4 −

10

3 −

10

2 −

10

1 −

10

Percentage PDF uncertainty 20 40 60 80 100 120 140 160 180 200

data

+-

,D no LHCb D data

+-

,D with LHCb D

, NNPDF3.0 NLO

2

=4 GeV

2

) ) for Q

2

( g(x,Q Δ

Impact of 7 TeV prompt-charm* results on the low-x gluon PDF:

Gauld, Rojo, Rittoli, Talbert [1506.0825] *LHCb-PAPER-2012-041: Nucl. Phys. B871 (2013) 1

SLIDE 10

10

Vector Boson + Jet

[GeV]

jet T

p

20 40 60 80 100 120 140

[1/GeV]

jet T

p d σ d σ 1

• 4

10

• 3

10

• 2

10

• 1

10

Data (stat.) Data (tot.) )

s

α ( O MSTW08, )

2 s

α ( O MSTW08, )

2 s

α ( O CTEQ10, )

2 s

α ( O NNPDF 2.3, POWHEG + PYTHIA:

= 7 TeV Data s > 10 GeV

jet T

p LHCb 1.2

Z

y

2.0 2.5 3.0 3.5 4.0 4.5

Z

dy σ d σ 1

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

Data (stat.) Data (tot.) )

s

α ( O MSTW08, )

2 s

α ( O MSTW08, )

2 s

α ( O CTEQ10, )

2 s

α ( O NNPDF 2.3,

POWHEG + PYTHIA: = 7 TeV Data s > 20 GeV

jet T

p LHCb

Jets @ LHCb: anti-kT, R=0.5, particle flow. First LHCb jet paper provides differential measurements of Z+jet production:

LHCb-PAPER-2013-058: JHEP 01 (2014) 33

σ(W+j)/σ(Zj) and σ(W-j)/σ(Zj) also measured integrated over LHCb acceptance for pT(j) > 20 GeV; these also agree with NLO SM predictions. Run 1 differential W+jet measurements are in preparation. Such measurements in Runs 2 & 3 will enable strongly constraining d/u at large-x.

LHCb-PAPER-2015-021 PRD 92 (2015) 052001 Farry, Gauld [1505.01399]

SLIDE 11

11

Jet Tagging

Use a SV-based algorithm to identify b and c jets (leveraging LHCb VELO):

[GeV]

cor

M SV

2 4 6 8 10

candidates

5000 10000

LHCb data b c udsg

candidates

Jet Tagging

200 400 600 800 1000

) udsg | bc BDT(

• 1
• 0.5

0.5 1

) c | b BDT(

• 1
• 0.5

0.5 1

LHCb data +jet D

light parton charm beauty Initial (no-tagging) sample: 70% light parton, 22% charm, 8% beauty.

example SV feature: “corrected mass”

JINST 10 (2015) P06013 LHCb-PAPER-2015-016

SV features used in 2 BDTs

Performance validated & calibrated using large heavy-flavor-enriched jet data

• samples. Two-D BDT distributions fitted to extract SV-tagged jet flavor

content; c-jet and b-jet yields each precisely determined simultaneously.

SLIDE 12

12

W+b & W+c

7TeV 8TeV

5 (Wj) [%] σ (Wq)/ σ

• 0.25

0.25 0.5 Charge Asymmetry LHCb MCFM (NLO) W+c W+b

Expect ~10x larger stats in Run 2; will be able to probe s vs s-bar PDFs using differential measurements of W+c. W+charm production probes the strange content of the proton. In the forward region, this includes large-x s vs s-bar.

PRD 92 (2015) 052001 LHCb-PAPER-2015-021

W + b-jet

qj qi b b W

W + c-jet

g s c W

SLIDE 13

13

Top

(top) [fb] σ

100 200 300 400

7TeV 8TeV

LHCb MCFM (NLO)

σ(top)[7 TeV] = 239 ± 53 (stat) ± 33 (syst) ± 24 (theory) fb , σ(top)[8 TeV] = 289 ± 43 (stat) ± 40 (syst) ± 29 (theory) fb .

Results for σ(tt+t+t-bar): Top production in the forward region probes the large-x gluon PDF and may be more sensitive to BSM. LHCb made the first observation of forward top production in Run 1:

<x1> ~ 0.2, <x2> ~ 0.02

PRL 115 (2015) 112001, LHCb-PAPER-2015-022

Expect ~20x more stats in Run 2; will explore separating pair and single-top production, and differential measurements. Should reduce the large-x gluon PDF uncertainty by ~20% [Gauld, 1311.1810].

Kagan, Kamenik, Perez, Stone [1103.3747]

SLIDE 14

14

Z+c

Boettcher, Ilten, MW [arxiv:1512.06666]

Whether there exists “intrinsic” (non-perturbative) charm content in the proton has long been debated. LHCb can say a lot here in Runs 2 and 3. Also effects Higgs production by ~2% (more for H+c), direct dark matter detection (assuming H exchange), and prompt atmospheric neutrino rates.

4.5

)

4.5

2 2.5 3 3.5 4 4.5

) Zj ( σ )/ Zc ( σ

0.04 0.06 0.08

CT14NNLO BHPS1 BHPS2 SEA1 SEA2

= 14 TeV s

• 1

Ldt = 15 fb

∫

) Z ( y

2 2.5 3 3.5 4 4.5

CT14NNLO IC

1 2 3

g c c Z

g c c Z

SLIDE 15

15

PDFs Summary

g c c Z

et

c W

small-x gluon large-x gluon large-x d/u intrinsic charm s vs s-bar W

g g s

SLIDE 16

16

Dijets

LHCb 7 TeV data SM H1504.02493L 100 GeV Axigluon

40 60 80 100 120 140 160

• 1

1 2 3 4 5 Mbb

_@GeVD

AC

b b@%D

Ab¯

b C ≡ N(∆y > 0) − N(∆y < 0)

N(∆y > 0) + N(∆y < 0),

b anti-b Di-heavy-flavor jet production provides a standard candle measurement, is useful for constraining tagging efficiencies, and probes BSM physics.

LHCb-PAPER-2014-023: PRL 113 (2014) 082003.

Expect much larger stats in Run 2; plan to also measure AC(cc), along with σ(bb) and σ(cc) differentially. y

SLIDE 17

Pomeron γ p p Υ(nS)

17

Quarkonia

LHCb has published detailed differential measurements of ψ, ϒ, ηc, xc,b states. One of the more unique ones is via Central Exclusive Production:

σ(γp) (pb) W (GeV)

LHCb sensitivity

LHCb (b)

LO NLO B.G. bCGC Gauss LC bCGC H1 2000 LHCb run 1 ZEUS 1998/2009

101 102 103 104 102 103

LHCb-PAPER-2015-011: JHEP 09 (2015) 084

LHCb has also measured associated production of J/ψ + open charm and double open charm (c-c and c-cbar); these data are qualitatively consistent with double-parton scattering.

LHCb-PAPER-2012-003: JHEP 01 (2013) 90 LHCb-PAPER-2015-046

SLIDE 18

18

Heavy Ions

y

• 4
• 2

2 4

pPb

R

0.2 0.4 0.6 0.8 1 1.2 1.4 = 5 TeV

NN

s pPb

LHCb

EPS09 at NLO in Ref.[3]

(1S) Υ ψ Prompt J/

(1S) Υ LHCb, ψ LHCb, Prompt J/ from b ψ LHCb, J/

Cold nuclear matter effects studied in Pb-p vs p-Pb, each compared to reference p-p data, show a large suppression in the forward region:

Pb-p vs p-Pb LHCb-PAPER-2014-015: JHEP 07 (2014) 094 LHCb-PAPER-2013-052: JHEP 02 (2014) 72

LHCb recently took Pb-Pb data too and we expect our heavy-ion program to continue to expand in the coming years.

L=1.6/nb Ref [3] is Albacete et al [1301.3395]

SLIDE 19

19

SMOG

In fixed-target mode, LHCb is a central-backward detector that probes energy densities between that of the SPS and RHIC. Data collected: p-He, p-Ne, p- Ar and Pb-Ne, Pb-Ar. LHCb developed the System for Measuring the Overlap with Gas to obtain a high-precision (1%) luminosity measurement by injecting a noble gas into the VELO to profile the beams -- but also permits running in fixed-target mode!

• )

2

dimuon invariant mass (MeV/c 2900 3000 3100 3200 3300 3400 3500

2

Events / 16 MeV/c 20 40 60 80 100 120

LHCb Preliminary p-Ne Collisions

2

1.2 MeV/c ± = 19.4 σ

2

1.4 MeV/c ± mean = 3094.1 17 ± = 293

signal

N

E(CM)=110 GeV (~20 hours of running)

SLIDE 20

Summary

LHCb is a general-purpose detector in the forward region.

SLIDE 21

SLIDE 22

22

Jet Tagging

JINST 10 (2015) P06013 LHCb-PAPER-2015-016

) udsg | bc BDT(

• 1
• 0.5

0.5 1

) c | b BDT(

• 1
• 0.5

0.5 1

LHCb simulation

• jets

b ) udsg | bc BDT(

• 1
• 0.5

0.5 1

) c | b BDT(

• 1
• 0.5

0.5 1

LHCb simulation

• jets

c ) udsg | bc BDT(

• 1
• 0.5

0.5 1

) c | b BDT(

• 1
• 0.5

0.5 1

LHCb simulation

• jets

udsg

T T

(jet) [GeV]

T

p

20 40 60 80 100

efficiency in data/simulation

0.6 0.8 1 1.2 1.4

LHCb )-jet b,c (

(jet) [GeV]

T

p

20 40 60 80 100

SV-tag efficiency

0.2 0.4 0.6 0.8 1

LHCb

• jet

b

• jet

c

Efficiencies are for 0.3% light-jet mis-tag.

SLIDE 23

23

Jet Tagging

JINST 10 (2015) P06013 LHCb-PAPER-2015-016

BDT distributions for b-jet enriched data.

100 200 300 400 500 600 700 800 900

) udsg | bc BDT(

• 1
• 0.5

0.5 1

) c | b BDT(

• 1
• 0.5

0.5 1

LHCb data +jet B

100 200 300 400 500 600 700 800 900

) udsg | bc BDT(

• 1
• 0.5

0.5 1

) c | b BDT(

• 1
• 0.5

0.5 1

LHCb fit ) udsg | bc BDT(

• 1
• 0.5

0.5 1

candidates

2000 4000

LHCb data b c udsg ) c | b BDT(

• 1
• 0.5

0.5 1

candidates

1000 2000 3000

LHCb data b c udsg

[GeV]

cor

M SV

2 4 6 8 10

candidates

1000 2000 3000 4000

LHCb data b c udsg

[GeV]

cor

M SV

2 4 6 8 10

candidates

5000 10000

LHCb data b c udsg

candidates

corrected mass in data for (top) b-jet enriched and (bottom) heavy-flavor enriched.

SLIDE 24

7TeV 8TeV

5 (Wj) [%] σ (Wq)/ σ

• 0.25

0.25 0.5 Charge Asymmetry LHCb MCFM (NLO) W+c W+b

0.5 0.6 0.7 0.8 0.9 1

Candidates/0.05

20000 40000

Data W Z Jets

= 8 TeV s ,

+

µ )

µ

j (

T

p )/ µ (

T

p

0.5 0.6 0.7 0.8 0.9 1 20000 40000

= 8 TeV s ,

−

µ LHCb

√

24

W+jet

PRD 92 (2015) 052001 LHCb-PAPER-2015-021

10 20 30 40 50 60 70 80 90

) udsg | bc BDT(

• 1
• 0.5

0.5 1

) c | b BDT(

• 1
• 0.5

0.5 1

LHCb data

[GeV]

cor

M SV

2 4 6 8 10

Candidates/0.5 GeV

500 1000

LHCb Data b c udsg

W from fits to muon isolation. Jet flavor from 2-D BDT fits. Run 1 results agree SM(CT10) predictions but stat limited. Expect much greater stats in Run 2; will be able to probe s vs s-bar PDFs using differential measurements.

SLIDE 25

25

W+Jet

Results SM prediction 7 TeV 8 TeV 7 TeV 8 TeV

σ(Wb) σ(Wj) × 102

0.66 ± 0.13 ± 0.13 0.78 ± 0.08 ± 0.16 0.74+0.17

−0.13

0.77+0.18

−0.13 σ(Wc) σ(Wj) × 102

5.80 ± 0.44 ± 0.75 5.62 ± 0.28 ± 0.73 5.02+0.80

−0.69

5.31+0.87

−0.52

A(Wb) 0.51 ± 0.20 ± 0.09 0.27 ± 0.13 ± 0.09 0.27+0.03

−0.03

0.28+0.03

−0.03

A(Wc) −0.09 ± 0.08 ± 0.04 −0.01 ± 0.05 ± 0.04 −0.15+0.02

−0.04

−0.14+0.02

−0.03 σ(W +j) σ(Zj)

10.49 ± 0.28 ± 0.53 9.44 ± 0.19 ± 0.47 9.90+0.28

−0.24

9.48+0.16

−0.33 σ(W −j) σ(Zj)

6.61 ± 0.19 ± 0.33 6.02 ± 0.13 ± 0.30 5.79+0.21

−0.18

5.52+0.13

−0.25

SLIDE 26

26

Top

Inclusive W+jet agrees with NLO SM from MCFM.

) [GeV] j + µ (

T

p +jet) W ( N

2000 4000 6000 8000

LHCb Data SM

20 45 70 95

∞

) [GeV] j + µ (

T

p Charge Asymmetry

• 0.4
• 0.2

0.2 0.4 20 45 70 95

∞

LHCb Data SM ) [GeV] c + µ (

T

p ) c + W ( N

50 100 150 200

Data SM LHCb

20 45 70 95

∞

Same for W+c.

SLIDE 27

27

(top) [fb] σ

100 200 300 400

7TeV 8TeV

LHCb MCFM (NLO)

Top

PRL 115 (2015) 112001 LHCb-PAPER-2015-022

ffiffi ffi

) [GeV] b + µ (

T

p ) W+b ( N

100 200

Data +top Wb Wb LHCb

20 45 70 95

∞

) [GeV] b + µ (

T

p Charge Asymmetry

• 0.4
• 0.2

0.2 0.4

Data +top Wb Wb LHCb

20 45 70 95

∞ σ(top)[7 TeV] = 239 ± 53 (stat) ± 33 (syst) ± 24 (theory) fb , σ(top)[8 TeV] = 289 ± 43 (stat) ± 40 (syst) ± 29 (theory) fb .

Data requires a top contribution (Wb validated in sidebands): Results for σ(tt+t+t):

_ _

SLIDE 28

28

Intrinsic Charm

Predicted Zc/Zj results shown above for LHCb for Runs (left) 2 and (right) 3. Potential impact on Higgs production in CMS/ATLAS show at right. For H+c (not shown), the effect of intrinsic charm is comparable to that of the SM charm Yukawa coupling!

BHPS1 BHPS2 SEA1 SEA2 0.95 1 1.05

H → gg CT14NNLO IC

0.95 1 1.05

H → VV

0.95 1 1.05

VH → pp

0.95 1 1.05

H t t → pp

2 2.5 3 3.5 4 4.5

) Zj ( σ )/ Zc ( σ

0.04 0.06 0.08

CT14NNLO BHPS1 BHPS2 SEA1 SEA2

= 13 TeV s

• 1

Ldt = 5 fb

∫

) Z ( y

2 2.5 3 3.5 4 4.5

CT14NNLO IC

1 2 3

2 2.5 3 3.5 4 4.5

) Zj ( σ )/ Zc ( σ

0.04 0.06 0.08

CT14NNLO BHPS1 BHPS2 SEA1 SEA2

= 14 TeV s

• 1

Ldt = 15 fb

∫

) Z ( y

2 2.5 3 3.5 4 4.5

CT14NNLO IC

1 2 3