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ZEUS Novosibirsk, Russia 15-19 June, 2015 O U T L I N E - - PowerPoint PPT Presentation

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Heavy flavour production at HERA Uri Karshon Weizmann Institute of Science, ISRAEL On behalf of the H1 and ZEUS Collaborations PHOTON-2015 Conference Budker Institute of Nuclear Physics, ZEUS Novosibirsk, Russia 15-19 June, 2015 O U T L I N

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SLIDE 1

Heavy flavour production at HERA Uri Karshon Weizmann Institute of Science, ISRAEL On behalf of the H1 and ZEUS Collaborations PHOTON-2015 Conference Budker Institute of Nuclear Physics, Novosibirsk, Russia 15-19 June, 2015

ZEUS O U T L I N E

Introduction and experimental set-up Theory of heavy quark production D∗± photoproduction at 3 center-of-mass energies Charm fragmentation fractions in photoproduction D± production in deep inelastic scattering HERA charm data combination in DIS Combination of D∗± differential cross sections in DIS Beauty production in DIS Summary

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SLIDE 2

Introduction and experimental set-up

e+ (k') e+ (k) proton (P) g (xgP) γ* (q) c c

_

W2

e±(k) + p(P) → e±(k′) + X; s = (P + k)2 Photon virtuality: Q2 = −q2 = −(k − k‘)2 Bjorken x: x =

Q2 2q·P ;

Inelasticity: y = q·P

k·P

Q2 = sxy; W = γ∗p CM energy Photoproduction (PHP): Q2 ≃ 0 GeV 2 (e± undetected) Deep Inelastic Scattering (DIS): Q2 > 1 or 5 GeV 2 (e± detected) BGF: Dominant process for c,b production in DIS Direct probe of gluon density in proton; Sensitivity to c,b quark masses

HERA

  • PETRA

DORIS HASYLAB

DESY

Halle NORD (H1) Hall NORTH (H1) Halle OST (HERMES) Hall EAST (HERMES) Halle SÜD (ZEUS) Hall SOUTH (ZEUS) Halle WEST (HERA-B) Hall WEST (HERA-B)

Elektronen / Positronen Electrons / Positrons Protonen Protons

  • Synchrotronstrahlung

Synchrotron Radiation

Hall nord (H1) Hall ouest (HERA-B) Hall est (HERMES)

Rayonnement Synchrotron

Hall sud (ZEUS)

Electrons / Positons

  • Protons
  • HERA: unique e±p collider with E(e±, p) = 27.6, 820/920 GeV

2 main experiments: H1, ZEUS 2 run periods: HERA I, HERA II 1995-2000 2003-2007 √s 318 (300) 318 GeV L 1.5 · 1031 7 · 1031 cm−2 s−1 Lint 126 373 pb−1 HERA II data taken ≈ half e+p and half e−p In 2007 two short runs at lower p energies: Ep = 575 GeV; Ep = 460 GeV

Heavy Flavour production at HERA

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SLIDE 3

Theory of heavy quark production

Several QCD NLO schemes for heavy quark (Q=c or b) production: 1)Massive scheme: Q2 ≈ m2

Q Fixed flavour number scheme (FFNS)

  • 3 active flavours in proton; Q-quark not considered as parton in p
  • c or b produced perturbatively in hard scattering (see p.2)
  • Mass effects correctly included
  • Spoiled by large logs of Q2/m2

Q, pt/mQ...

2)Massless scheme: Q2 >> m2

Q

Zero-mass variable flavour number scheme (ZM-VFNS)

  • c or b treated as massless parton
  • Resummation of large logarithms of Q2/m2

Q

  • ⇒ c or b density added as 4th flavour like the light quarks

At intermediate Q2 the 2 schemes should be merged 3) General-mass variable flavour number scheme (GM-VFNS)

  • Equivalent to FFNS for Q2 ≤ m2

Q and to ZM-VFNS for Q2 > m2 Q

  • Interpolation in between (various schemes interpolate differently)
  • Used in parton density function (PDF) fits (useful at LHC)

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SLIDE 4

D∗± photoproduction at 3 CM energies

Clear D∗± signals seen in M(K−π+π+

s ) − M(K−π+) distributions

at 3 different CM energies: √s = 318, 251, 225 GeV in the kinematic region: 1.9 < pD∗

T

< 20 GeV ; |ηD∗| < 1.6 ; Q2 < 1 GeV2 ; 0.167 < y < 0.802 JHEP 10 (2014) 003 HER: L = 144 pb−1 MER: L = 6.3 pb−1 LER: L = 13.4 pb−1

) (GeV) π )-M(K

s

π π M(K 0.14 0.145 0.15 0.155 0.16 0.165 0.17 Entries 1000 2000 3000 4000 5000 6000

ZEUS

s

π π K → D*

= 318 GeV) s (

  • 1

ZEUS 144 pb Wrong-sign combinations Signal region Background fit (correct-sign) Background fit (wrong-sign)

ZEUS

) (GeV) π )-M(K

s

π π M(K 0.14 0.145 0.15 0.155 0.16 0.165 0.17 Entries 20 40 60 80 100 120 140 160 180 200 220 240

ZEUS

s

π π K → D*

= 251 GeV) s (

  • 1

ZEUS 6.3 pb Wrong-sign combinations Signal region Background fit (correct-sign) Background fit (wrong-sign)

ZEUS

) (GeV) π )-M(K

s

π π M(K 0.14 0.145 0.15 0.155 0.16 0.165 0.17 Entries 50 100 150 200 250 300 350 400

ZEUS

s

π π K → D*

= 225 GeV) s (

  • 1

ZEUS 13.4 pb Wrong-sign combinations Signal region Background fit (correct-sign) Background fit (wrong-sign)

ZEUS

N(D∗) = 12256 ± 191 N(D∗) = 417 ± 37 N(D∗) = 859 ± 49 Background estimated by fitting simultaneously correct- and wrong-sign distributions in the range ∆M < 0.168 GeV

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D∗± photoproduction at 3 CM energies Visible D∗ PHP cross sections obtained from: σvis(D∗) = Ndata(D∗)

A·BR·L

BR = B(D∗ → D0π) · B(D0 → Kπ) = 0.0263; A = acceptance Ratio of visible cross sections: Rσ =

σi σHER; i = HER, MER, LER

yields higher precision of E-dependence of cross section since some syst. uncertainties in data and theory cancel Data compared to FFNS NLO predictions:

(GeV) s

240 260 280 300 320

σ

R

0.2 0.4 0.6 0.8 1 1.2

ZEUS

0.167 < y < 0.802 < 20 GeV

D* T

1.9 < p | < 1.6

D*

η |

2

< 1 GeV

2

Q = 〉 W 〈 136 GeV 152 GeV 192 GeV D* X → ZEUS ep NLO QCD

Total syst. uncertainty ≈ 5% in data few % in theory < W > = mean W from generated MC MER/LER cross sections similar HER cross section higher Cross sections increase with increasing ep CM energy This increase is predicted by NLO QCD

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Charm fragmentation fractions in PHP

Fragmentation fractions of c-quarks into charm hadrons: Probability of c quark to hadronise into a given charm hadron

f(c → charm hadron) = σ(charm hadron)/σ(total charm production)

Needed to go from partonic QCD to hadronic cross sections No QCD predictions; crucial to compare pQCD with measurements Are they the same for c-quarks produced in e+e−, ep, pp collisions ? Test fragmentation universality by measuring all of them Measurements performed in PHP regime: Q2 < 1 GeV2 Charm hadrons reconstructed in the range: pT > 3.8 GeV, |η| < 1.6, 130 < W < 300 GeV Charm hadrons measured: D0 → K−π+, D+ → K−π+π+ D∗+ → D0π+

s → K−π+π+ s

D+

s → φπ+,

Λ+

c → K−pπ+

σtot = σeq(D0) + σeq(D+) + σ(D+

s ) + 1.14 σ(Λ+ c )

Full HERA II data: 372 pb−1 JHEP 09 (2013) 058

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SLIDE 7

Charm fragmentation fractions in PHP Silicon-strip detector used for charm vertices ⇒ Clear charm hadron signals for all channals

Charm fragmentation fractions 0.1 0.2 0.3 0.4 0.5 0.6 0.7

p γ ZEUS HERA II p γ ZEUS HERA I ep DIS ZEUS HERA I ep DIS H1

  • e

+

e

) D → f (c )

+

D → f (c )

+

D* → f (c )

s

D → f (c )

c

Λ → f (c

Charm fragmentation fractions: Results (left column) in good agreement with previous results:

ZEUS PHP, ZEUS DIS, H1 DIS, e−e−

Precision of charm f.f. competitive with combined e+e− LEP results Fragmentation fractions of c-quarks independent of production Support hypothesis of universality of heavy-quark fragmentation Universality supported also by new LHC pp data (ALICE + LHCb)

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D± production in DIS

)

2

(GeV

2

Q

10

2

10

3

10

)

2

(nb/GeV

2

/dQ σ d

  • 4

10

  • 3

10

  • 2

10

  • 1

10 1

  • 1

354 pb

+

ZEUS D

  • 1

133.6 pb

+

ZEUS D HVQDIS

ZEUS

y

0.1 0.2 0.3 0.4 0.5 0.6 0.7

/dy (nb) σ d

2 4 6 8 10 12 14 16 18 20

  • 1

354 pb

+

ZEUS D HVQDIS

ZEUS

) (GeV) π π M(K 1.7 1.75 1.8 1.85 1.9 1.95 2 2.05 2.1 Combinations / 10 MeV 500 1000 1500 2000 2500 3000 3500 4000 4500

ZEUS

  • 1

354 pb

+

ZEUS D + background

mod

Gauss

) (GeV)

+

(D

T

p

2 3 4 5 6 7 8 9 10

) (nb/GeV)

+

(D

T

/dp σ d

  • 2

10

  • 1

10 1

  • 1

354 pb

+

ZEUS D

  • 1

133.6 pb

+

ZEUS D HVQDIS

ZEUS

)

+

(D η

  • 1.5
  • 1
  • 0.5

0.5 1 1.5

) (nb)

+

(D η /d σ d

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

  • 1

354 pb

+

ZEUS D

  • 1

133.6 pb

+

ZEUS D HVQDIS

ZEUS

Full HERA II data: 354 pb−1 JHEP 05 (2013) 023 Clean D+ signal N(D+) = 8356 ± 198 D+ differential cross sections w.r.t Q2, y, pT(D+), η(D+) in kinematic region 5 < Q2 < 1000 GeV2, 1.5 < pT(D+) < 15 GeV, |η(D+)| < 1.6, 0.02 < y < 0.7

NLO QCD predictions based on FFNS describe data well up to Q2 ≈ 1000 GeV2 Similar agreement for double differential cross sections dσ/dy for different Q2 ranges

Heavy Flavour production at HERA

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SLIDE 9

D± production in DIS

0.2 0.4 0.2 0.4 10

  • 4

10

  • 3

10

  • 2

0.2 0.4 10

  • 4

10

  • 3

10

  • 2

ZEUS

F2

cc

Q2 = 6.5 GeV2 Q2 = 20.4 GeV2 Q2 = 35 GeV2 Q2 = 60 GeV2

x

Q2 = 200 GeV2

x

ZEUS D+ 354 pb-1 ZEUS D* 81.9 pb-1 HERAPDF1.5 ZEUS-S PDF

Charm contribution to proton structure function: Express double differential cross section as:

d2σc¯

c

dxdQ2 = 2πα2 xQ4 [(1 + (1 − y)2)F c¯ c 2 − y2F c¯ c L ]

F c¯

c 2 , F c¯ c L are charm contributions to

proton structure functions F2 and FL dσ/dy for different Q2 bins used to extract F c¯

c 2

at reference points xi, Q2

i for each bin i using

F c¯

c 2,meas(xi, Q2 i) = σi,meas F c¯

c 2,theo(xi,Q2 i )

σi,theo

F2,theo and σi,theo calculated at NLO in FFNS with HVQDIS program D± results compared to previous ZEUS D∗ results and to predictions of GM-VFNS based on HERAPDF1.5 parton densities and of FFNS based on ZEUS-S PDF HERAPDF1.5 uses HERA ep data to provide NLO predictions compatible with other PDF groups

The NLO calculations describe new precise data well

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SLIDE 10

HERA charm data combination in DIS

Combined 9 data sets of D∗, D+, D0, µ and liftime tag data with 155 H1 and ZEUS cross section measurements from various HERA I and HERA II analyses EPJ C73 (2013) 2311

Charm reduced cross section, σc¯

c red, obtained in kinematic range:

2.5 < Q2 < 2000 GeV2; 3 · 10−5 < x < 5 · 10−2

d2σc¯

c

dxdQ2 = 2πα2 xQ4 [(1 + (1 − y)2)σc¯ c red]

Q2=18 GeV2 HERA

H1 and ZEUS

H1 VTX H1 D* HERA-II H1 D* HERA-I ZEUS c → µ X ZEUS D* 98-00 ZEUS D* 96-97 ZEUS D0 ZEUS D+

x σ

red cc _

10-3 10-2 0.2 0.4 0.6

Reduced cross sections σc¯

c red

as function of x for fixed Q2 values: Example for Q2 = 18 GeV2 Combined results - filled circles Correlated systematics fully taken into account Combined results uncertainty ≈ factor 2

better than each most precise data set in the combination

Heavy Flavour production at HERA

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SLIDE 11

HERA charm data combination in DIS How well does the mixed massive-massless scheme GM-VFNS work? Reduced cross sections σc¯

c red as function of x for fixed Q2 values

0.2

2

=2.5 GeV

2

Q 0.2

2

= 5 GeV

2

Q 0.2

2

= 7 GeV

2

Q 0.5

2

=12 GeV

2

Q 0.5

2

=18 GeV

2

Q 0.5

2

=32 GeV

2

Q 0.5

2

=60 GeV

2

Q 0.5

2

=120 GeV

2

Q 0.5

2

=200 GeV

2

Q 0.5

2

=350 GeV

2

Q 0.5

2

=650 GeV

2

Q 0.5

2

=2000 GeV

2

Q red c c

σ

0.2 0.5 0.5 0.5

  • 4

10

  • 3

10

  • 2

10

  • 4

10

  • 3

10

  • 2

10

x

  • 4

10

  • 3

10

  • 2

10

HERA HERAPDF1.5

H1 and ZEUS

Combined inclusive DIS data (HERA I+II) compared to NLO predictions based

  • n HERAPDF1.5 extracted in

RT standard scheme Lines are predictions with Mc = 1.4 GeV Mc = effective (not physical) mass parameter in GM-VFNS Large theory uncertainty dominated by Mc variation Within uncertainties NLO GM-VFNS describe data well

Heavy Flavour production at HERA

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SLIDE 12

HERA charm data combination in DIS

Combined NLO analysis with σc¯

c red and inclusive DIS cross sections

in kinematic range:

W > 15 GeV, x < 0.65, Q2 > 3.5 GeV2

For each HFL scheme, PDF fits performed with 1.2 < Mc < 1.8 GeV χ2 values vs. Mc from PDF fits for various HFL schemes VFNS predictions for σc¯

c red with

Mc = 1.4 GeV (up) and Mc = M opt

c

(down)

[GeV]

c

M

1.2 1.4 1.6 1.8

)

c

(M

2

χ

600 650 700 750

RT standard RT optimised ACOT-full χ S-ACOT- ZM-VFNS

  • pt

C

M

H1 and ZEUS

Charm + HERA-I inclusive

Minimal χ2 values observed for each scheme at different M opt

c

Data described much better with M opt

c

than with fixed Mc Predictions of all schemes are very similar for Q2 ≥ 5 GeV2

Heavy Flavour production at HERA

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SLIDE 13

HERA charm data combination in DIS Implications on NLO predictions for W, Z production at LHC W +, W −, Z0 cross section predictions for LHC at √s = 7 TeV Calculated for each scheme for 1.2 < Mc < 1.8 GeV in 0.1 GeV steps

[GeV]

c

M 1.2 1.4 1.6 1.8

[nb]

+

W

σ

54 56 58 60 62 64

  • pt

C

M

RT standard RT optimised ACOT-full χ S-ACOT- ZM-VFNS

= 7 TeV s Charm + HERA-I inclusive

H1 and ZEUS [GeV]

c

M 1.2 1.4 1.6 1.8

[nb]

  • W

σ

38 40 42 44

  • pt

C

M

RT standard RT optimised ACOT-full χ S-ACOT- ZM-VFNS

= 7 TeV s Charm + HERA-I inclusive

H1 and ZEUS [GeV]

c

M 1.2 1.4 1.6 1.8

[nb]

Z

σ

27 28 29 30 31 32

  • pt

C

M

RT standard RT optimised ACOT-full χ S-ACOT- ZM-VFNS

= 7 TeV s Charm + HERA-I inclusive

H1 and ZEUS

All cross sections rise monotonically with Mc Significant spread of ≈ 6% between predictions for any fixed Mc Reduces to ≈ 1.4 − 2% when taking M opt

c

for each scheme

Heavy Flavour production at HERA

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SLIDE 14

HERA charm data combination in DIS Combined charm data vs. ABM FFNS prediction: Uses instead

  • f pole mass the running mass definition in MS scheme

0.2 0.5 0.5 0.5

σ

red cc _

H1 and ZEUS

Q2=2.5 GeV2 Q2=5 GeV2 Q2=7 GeV2 Q2=12 GeV2 Q2=18 GeV2 Q2=32 GeV2 Q2=60 GeV2 Q2=120 GeV2 Q2=200 GeV2 Q2=350 GeV2

10-4 10-3 10-2

Q2=650 GeV2

10-4 10-3 10-2

Q2=2000 GeV2 HERA

ABM09NNLO MS



ABM09NLO MS



10-4 10-3 10-2

x

Data well described in full kinematic region Similar NLO/NNLO predictions Less sensitivity to higher order corrections)

mc(mc) extraction in MS scheme: Same minimisation procedure as for VFNS

) [GeV]

c

(m

c

m

1 1.2 1.4 1.6

2

χ

620 640 660 680 700

FF (ABM)

H1 and ZEUS

Charm + HERA-I inclusive 0.05 GeV ± )=1.26

c

(m

c

m

mc(mc) = 1.26 ± 0.05exp. ± 0.03mod. ±0.02param. ± 0.02αs GeV Uncertainties are experimental, model, parametrisation and αs Consistent with PDG: 1.275 ± 0.025 GeV

Heavy Flavour production at HERA

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SLIDE 15

HERA charm data combination in DIS Measurement of running mc

[GeV] µ

1 10

) [GeV]

c

(m

c

m

0.8 1 1.2 1.4 1.6 1.8 2

H1 and ZEUS preliminary

HERA (prel.) PDG with uncertainty

[GeV] µ

1 10

) [GeV] µ (

c

m

0.4 0.6 0.8 1 1.2 1.4 1.6

H1 and ZEUS preliminary

HERA (prel.) PDG with evolved uncertainty

Extract mc(mc) separately for 6 different kinematic ranges in µ =

  • < Q2 > +4mc(mc)2

< Q2 > is the logarithmic average Q2

  • f the subset

Red points at scale mc and bands are PDG average mc(mc) translated to mc(µ) by:

mc(µ) = mc(mc)

(αs(µ)

π

)β−1 (αs(mc)

π

)β−1

β0 = 9/4 for Nf = 3

Data consistent with expected QCD running First measurement of mc(µ) from combined HERA charm reduced cross section data Important consistency check, similar to running mb at LEP EPJ C55 (2008) 525

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SLIDE 16

Combination of D∗± differential cross sections in DIS

Combined H1+ZEUS D∗+ visible differential cross sections w.r.t pD∗

T , ηD∗

hep-ex 1503.06042; JHEP to be published

(D*) (nb/GeV)

T

/dp σ d

  • 4

10

  • 3

10

  • 2

10

  • 1

10 1 (D*) (GeV)

T

p 2 3 4 5 6 7 8 9 10 20 ratio to HERA 0.8 1 1.2

2

< 1000 GeV

2

5 < Q 0.02 < y < 0.7 (D*) > 1.5 GeV

T

p (D*)| < 1.5 η |

HERA H1 ZEUS

X H1 and ZEUS

±

eD* → ep

(D*) η

  • 1.5
  • 1
  • 0.5

0.5 1 1.5 (D*) (nb) η /d σ d 1 2

2

< 1000 GeV

2

5 < Q 0.02 < y < 0.7 (D*) > 1.5 GeV

T

p (D*)| < 1.5 η |

HERA H1 ZEUS

X H1 and ZEUS

±

eD* → ep

Correlations in systematic uncertainties fully taken into account Impressive reduction of uncertainties in the combined results Precision of combined data ≈ 5% in large fraction of phase space Similar results and precision obtained for dσ/dQ2 and dσ/dy

Heavy Flavour production at HERA

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SLIDE 17

Combination of D∗± differential cross sections in DIS

Differential cross sections compared to NLO predictions: HVQDIS HVQDIS setup for ep → c¯ cX → D∗X uses some arbitrary variable definition e.g. µr = µf =

  • Q2 + 4m2

c

; mpole

c

= 1.5 GeV Try to change parameters such that normalisation and shapes of all differential cross sections describe the data well Found this to happen with µr = 0.5

  • Q2 + 4m2

c

; mpole

c

= 1.4 GeV and with some softening of the fragmantation function used (Kartvelishvili et al.) All other parameters left at default values The value of mpole

c

= 1.4 GeV was also found to describe better the data in the study of σc¯

c red (p.14)

”NLO QCD customised” shown as red dots in the following plots This is NOT a prediction, but may hint at which direction theory can be improved

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SLIDE 18

Combination of D∗± differential cross sections in DIS

HERA D∗+ differential cross sections w.r.t pD∗

T , ηD∗, Q2, y vs. theory (HVQDIS)

Negligible theoretical uncertainties in data points, since no extrapolation

(D*) (nb/GeV)

T

/dp σ d

  • 4

10

  • 3

10

  • 2

10

  • 1

10 1 (D*) (GeV)

T

p 2 3 4 5 6 7 8 9 10 20 ratio to HERA 0.6 0.8 1 1.2

HERA-II NLO QCD NLO QCD customised

±

D* → NLO QCD b

2

< 1000 GeV

2

5 < Q 0.02 < y < 0.7 (D*) > 1.5 GeV

T

p (D*)| < 1.5 η |

X H1 and ZEUS

±

eD* → ep

(D*) η

  • 1.5
  • 1
  • 0.5

0.5 1 1.5 (D*) (nb) η /d σ d 1 2

HERA-II NLO QCD NLO QCD customised

±

D* → NLO QCD b

2

< 1000 GeV

2

5 < Q 0.02 < y < 0.7 (D*) > 1.5 GeV

T

p (D*)| < 1.5 η |

X H1 and ZEUS

±

eD* → ep

)

2

(nb/GeV

2

/dQ σ d

  • 5

10

  • 4

10

  • 3

10

  • 2

10

  • 1

10 1 )

2

(GeV

2

Q 10

2

10

3

10 ratio to HERA 0.6 0.8 1 1.2 1.4

HERA-II NLO QCD NLO QCD customised

±

D* → NLO QCD b

2

< 1000 GeV

2

5 < Q 0.02 < y < 0.7 (D*) > 1.5 GeV

T

p (D*)| < 1.5 η |

X H1 and ZEUS

±

eD* → ep

y 0.1 0.2 0.3 0.4 0.5 0.6 0.7 /dy (nb) σ d 10 20

HERA-II NLO QCD NLO QCD customised

±

D* → NLO QCD b

2

< 1000 GeV

2

5 < Q 0.02 < y < 0.7 (D*) > 1.5 GeV

T

p (D*)| < 1.5 η |

X H1 and ZEUS

±

eD* → ep

Combined data reach precision of ≈ 5% NLO describe data within large uncertainties (≈ 10 − 30%) NLO customised describe data very well NNLO calculations and improved fragmentation models may help Similar conclusions for D∗ double-differential cross sections in Q2, y

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SLIDE 19

Beauty production in DIS

(GeV)

jet T

E

5 10 15 20 25 30 35 40

Entries

1 10

2

10

3

10

(GeV)

jet T

E

5 10 15 20 25 30 35 40

Entries

1 10

2

10

3

10

jet

η

  • 1.5 -1 -0.5 0 0.5

1 1.5 2 2.5

Entries

100 200 300 400 500

jet

η

  • 1.5 -1 -0.5 0 0.5

1 1.5 2 2.5

Entries

100 200 300 400 500

)

2

/GeV

2

(Q

10

log

0.5 1 1.5 2 2.5 3

Entries

50 100 150

)

2

/GeV

2

(Q

10

log

0.5 1 1.5 2 2.5 3

Entries

50 100 150

x

10

log

  • 4.5 -4 -3.5 -3 -2.5 -2 -1.5 -1

Entries

100 200 300

x

10

log

  • 4.5 -4 -3.5 -3 -2.5 -2 -1.5 -1

Entries

100 200 300

ZEUS

< 6 GeV, |S|>8

vtx

2 < m

  • 1

ZEUS 354 pb Monte Carlo LF Charm Beauty

)

2

(GeV

2

Q

10

2

10

3

10

)

2

(pb / GeV

2

/ dQ σ d

  • 2

10

  • 1

10 1 10

2

10

  • 1

ZEUS 354 pb

had

C × HVQDIS+ZEUS-S

had

C × HVQDIS+ABKM Rapgap x 1.49

ZEUS

e jet X → X b e b → ep )

2

(GeV

2

Q

10

2

10

3

10

Data / HVQDIS

0.5 1 1.5 2

′ ′ ′

x

  • 4

10

  • 3

10

  • 2

10

  • 1

10

/ dx (pb) σ d

3

10

4

10

5

10

6

10

7

10

  • 1

ZEUS 354 pb

had

C × HVQDIS+ZEUS-S

had

C × HVQDIS+ABKM Rapgap x 1.49

ZEUS

e jet X → X b e b → ep x

  • 4

10

  • 3

10

  • 2

10

  • 1

10

Data / HVQDIS

0.5 1 1.5 2

′ ′ ′

JHEP 09 (2014) 127 Beauty cross section at HERA much smaller than charm With a micro-vertex detector at HERA II, lifetime information can be used Ejet

T , ηjet, Q2, x distributions of sec. vertices

for b-enriched sample with 2 < mvtx < 6 GeV and |S| = |d/δd| > 8 d=decay length Differential cross sections for inclusive jet production in b-events as function of Q2 and x Good description of the data by the NLO FFNS HVQDIS prediction

Heavy Flavour production at HERA

  • U. Karshon

19

slide-20
SLIDE 20

Beauty production in DIS

)

2

(GeV

2

Q

10

2

10

3

10

+ 0.03 i

b b 2

F

0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2 0.22

  • 1

ZEUS vtx 354 pb

  • 1

ZEUS e 363 pb

  • 1

114 pb µ ZEUS

  • 1

+vtx 126 pb µ ZEUS

  • 1

H1 vtx 246 pb HERAPDF 1.5 ABKM NNLO MSTW08 NLO MSTW08 NNLO CTEQ6.6 NLO JR09

x=0.032 i=0 x=0.013 i=1 x=0.005 i=2 x=0.002 i=3 x=0.0013 i=4 x=0.0005 i=5 x=0.0002 i=6 x=0.00013 i=7

  • 3

0.005 0.01 0.015 0.02

  • 3

0.005 0.01 0.015 0.02

  • 3

0.005 0.01 0.015 0.02 0.02 0.04 0.02 0.04 0.02 0.04 0.01 0.02 0.03

x

  • 4

10

  • 3

10

  • 2

10

x

  • 4

10

  • 3

10

  • 2

10

x

  • 4

10

  • 3

10

  • 2

10 b b r

σ

0.005 0.01 0.015 0.02 0.02 0.04 0.01 0.02 0.03

  • 1

ZEUS 354 pb =4.07 GeV (best fit)

b

QCD fit, m =3.93 GeV

b

QCD fit, m =4.21 GeV

b

QCD fit, m

ZEUS

2

= 6.5 GeV

2

Q

2

= 12 GeV

2

Q

2

= 25 GeV

2

Q

2

= 30 GeV

2

Q

2

= 80 GeV

2

Q

2

= 160 GeV

2

Q

2

= 600 GeV

2

Q

Left: Structure function F b¯

b 2

as function of Q2 for fixed x values in good agreement with FFNS and GM-VFNS NLO and NNLO predictions Right: Reduced b cross section σb¯

b r as function of x for fixed Q2 values used

to determine b-quark mass in a QCD fit as done for the c-quark mass Lines are results with mb = 4.07 (best fit), 3.93 and 4.21 GeV

Sensitivity to mb comes mostly from low Q2

Heavy Flavour production at HERA

  • U. Karshon

20

slide-21
SLIDE 21

Beauty production in DIS

) (GeV)

b

(m

b

m 3.5 3.6 3.7 3.8 3.9 4 4.1 4.2 4.3 4.4 4.5 2

χ

586 588 590 592 594 596 598 600

ZEUS

Inclusive DIS + beauty QCD fit

mb(mb) = 4.07 ± 0.14(fit)+0.01

−0.07(mod.)+0.05 −0.00(param.)+0.08 −0.05(theo.) GeV

PDG: 4.18 ± 0.03 GeV from lattice QCD + time-like processes Extraction of mb(mb) from NLO FFNS fit using MS scheme Uncertainties are from fit, model, PDF parametrisation and theory mb(mb) translated, as for mc(mc), to mb(µ) with µ = 2mb and compared to PDG and LEP results

Mass running is consistent with QCD

Heavy Flavour production at HERA

  • U. Karshon

21

slide-22
SLIDE 22

Summary

H1 and ZEUS still providing new charm(ing) and beauty(full) results with full HERA data ⇒ tighter constraints on QCD σ(D∗) in PHP vs. ep CM energy measured for the first time at HERA. The D∗ cross sections increase with √s as predicted by NLO QCD New precise charm fragmentation fractions measurements in PHP competitive with e+e− collisions; support fragmentation universality New DIS charm measurements and HERA charm data combination provide constraints on PDFs and on QCD heavy quark calculations Most HERA DIS charm data were combined: Consistent data sets extracted using different methods; reduced uncertainties Data are well described by FFNS and GM-VFNS QCD predictions Optimal Mc parameter for different VFNS improves predictions of σW,Z at LHC Running charm mass in MS FFNS: mc(mc) = 1.26 ± 0.06 GeV agree with PDG First measurement of the charm-mass running at HERA Combination of D∗ visible cross sections: Negligible theory uncertainties (no extrapolation) Challenge to theory and fragmentation models New precise b-jet measurement + lifetime tag in DIS using secondary vertices: Data well described by NLO QCD b mass measured in MS scheme: mb(mb) = 4.07 ± 0.17 GeV agree with PDG b mass running consistent with QCD

Heavy Flavour production at HERA

  • U. Karshon

22