[PPT] - Results on the proton structure from HERA Shima Shimizu (CERN) PowerPoint Presentation

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Results on the proton structure from HERA

Shima Shimizu (CERN)

7/Jan/2011 @ KEK

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2

The world only e-p collider: HERA

Beam energy

proton :

(460, 575, 820,) 920 GeV

electron/positron:

27.5 GeV

ZEUS H1

electron proton

center of mass energy A unique collider at DESY, Hamburg Circumference: 6.3 km Operated since 1992 to 2007 2 collider experiments: H1 & ZEUS

DESY, Hamburg

GeV 318 ~) 225 ( = s

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3

History of HERA

1992-2000: HERA-I

(started with Ep=820GeV, until 1997) Make full use of large kinematic region. 1.5GeV2<Q2<30000GeV2

2002-2007: HERA-II

– High luminosity to collect high- Q2 data. (high-Q2 ↔ Weak boson exchange) – lepton beams are polarized. – Reduced Ep runs at the end.

HERA delivered

100 200 300 400 500 600 700 800 500 1000 1500 2000 2500

days of running Integrated Luminosity (pb

1)

days of running Integrated Luminosity (pb

1)

days of running Integrated Luminosity (pb

1)

days of running Integrated Luminosity (pb

1)

Luminosity upgrade (2000-2002) 820 GeV 920 GeV Low Ep

In total, each H1 and ZEUS gains ~0.5 fb-1.

HERA I HERA II

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4

Kinematic variables to describe DIS Q2: Virtuality probing power x : Bjorken scaling variable momentum fraction of struck quark y : Inelasticity

Deep Inelastic Scattering (DIS)

2 2 2

) (

'

k k q Q − − = − = q p Q x ⋅ = 2

2

k p q p y ⋅ ⋅ =

sxy Q =

2

: center of mass energy

s

Inclusive DIS cross sections can be written with structure functions.

⎥ ⎦ ⎤ ⎢ ⎣ ⎡ − =

+ − + + ±

) , ( ) , ( ) , ( 2 ) (

2 3 2 2 2 2 4 2 2 2

Q x xF Y Y Q x F Y y Q x F Y Q dxdQ p e d

L

m πα σ

) 1 ( 1

2

y Y − ± =

±

cross section with point-like particle Structure functions reflect momentum distribution of partons in the proton.

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5

Structure functions and PDFs

Structure functions are used for determination of the parton distribution functions (PDFs), q(x,Q2) and g(x,Q2)

F2

: [Sea + valence] quarks, (gluon)

FL

: longitudinal structure function

xF3 : parity violation term (Electroweak)

∑

+ = ) (

2

q q x A F

q

∑

− = ) (

3

q q x B xF

q

Valence quarks gluon (see later)

xg Q F ∝ ∂ ∂

2 2

ln

The Q2 evolution can be described by perturbative QCD, using DGLAP equation.

) , ( ) , ( ) , ( 2 ) (

2 3 2 2 2 2 2 2 2 4

Q x xF Y Y Q x F Y y Q x F dxdQ d Y Q p e

L r + − + + ±

− = = m σ πα σ

Measured quantity: reduced cross section DGLAP evolution

sizable only at high y high Q2 only

) 1 ( 1

2

y Y − ± =

±

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6

Z0 introduces parity violation.

valence quark

∑

− ∝ ) (

3

q q x xF

DIS at HERA

Pure proton target Free from target correction, nuclear effect.

y=1 (HERA √s=320 GeV)

x Q2 (GeV2)

E665, SLAC CCFR, NMC, BCDMS, Fixed Target Experiments: ZEUS H1

10

1

1 10 10 2 10 3 10 4 10 5 10

6

10

5

10

4

10

3

10

2

10

1

1

valence sea, gluon

Fixed target experiments γ Sea + valence quark Neutral current DIS (NC) at low Q2 γ exchange

∑

+ ∝ ) (

2

q q x F

xg Q F ∝ ∂ ∂

2 2

ln

gluon Charged current DIS (CC) W± exchange Charge selective interaction e- : u quark e+: d quark Neutral current DIS (NC) at high Q2 γ,Z0 exchange Sea + valence quark

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7

DIS in the detectors

Kinematic variables are reconstructed by two of measured variables;

energy scattered electron angle jet (~ struck quark) e+/- e+/- p p ν Neutral current (NC) process γ/Z0 exchange epe’X Charged current (CC) process W+- exchange epνX e’ jet jet

f

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HERA I inclusive DIS cross sections and HERA PDF1.0

published: JHEP01 (2010) 109

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9

Combining H1 and ZEUS cross sections

Combining all the HERA-I inclusive DIS cross sections from H1 and ZEUS: HERA I: e+p ~100pb-1, e-p ~16pb-1 NC: 0.045 < Q2 < 30000 GeV2, CC: 280 < Q2 < 30000 GeV2 1402 points (14 papers) After combination: 741 points Combination is done by averaging each data point by simultaneous χ2 fit. Assumption: H1 and ZEUS measure the same cross sections. Taking account of correlated systematics within/between experiments. Different detectors and analysis techniques bring different sensitivities to similar sorce of correlated systematic uncertainties. Cross calibration of experiments Reduction of systematic uncertainties.

JHEP01 (2010) 109

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10

Combining H1 and ZEUS cross sections

Uncertainty gets improved by more than sqrt(2). Main reduction in systematic uncertainties.

H1 and ZEUS

Q2 / GeV2 σr,NC(x,Q2)

x=0.0002 x=0.002 x=0.008 x=0.032 x=0.08 x=0.25

HERA I NC e+p ZEUS H1

+

0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1 10 10

2

10

3

10

4

JHEP01 (2010) 109

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Combined inclusive DIS cross sections

Precision of 1-2% for 3 < Q2 < 500 GeV2. Scaling violation is clearly seen.

H1 and ZEUS

x = 0.00005, i=21 x = 0.00008, i=20 x = 0.00013, i=19 x = 0.00020, i=18 x = 0.00032, i=17 x = 0.0005, i=16 x = 0.0008, i=15 x = 0.0013, i=14 x = 0.0020, i=13 x = 0.0032, i=12 x = 0.005, i=11 x = 0.008, i=10 x = 0.013, i=9 x = 0.02, i=8 x = 0.032, i=7 x = 0.05, i=6 x = 0.08, i=5 x = 0.13, i=4 x = 0.18, i=3 x = 0.25, i=2 x = 0.40, i=1 x = 0.65, i=0

Q2/ GeV2 σr,NC(x,Q2) x 2i

+

HERA I NC e+p Fixed Target HERAPDF1.0

10

3

10

2

10

1

1 10 10 2 10 3 10 4 10 5 10 6 10 7 1 10 10

2

10

3

10

4

10

5

Low x High x JHEP01 (2010) 109

xg Q F ∝ ∂ ∂

2 2

ln

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12

HERA PDF 1.0

Data sets Combined HERA I inclusive DIS cross sections e-p CC, e+p CC, e-p NC (Q2>100GeV2), e+p NC (Q2> Q2

min)

Settings PDF parameterized at the starting scale Q0

2

Central fit has 10 free parameters: chosen by saturation of χ2 RT-VFN scheme NLO DGLAP evolution using QCDNUM17.02 Scales: μR= μF= Q2

c u U + = b s d D + + =

4.75 mb (GeV) 1.9 Q0

2 (GeV2)

3.5 Q2

min (GeV2)

1.4 mc (GeV) 0.31 fs=s/D 0.1176 αS(MZ)

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13

0.2 0.4 0.6 0.8 1

4

10

3

10

2

10

1

10 1 0.2 0.4 0.6 0.8 1 HERAPDF1.0

exp. uncert.

model uncert. parametrization uncert.

x xf

2

= 10 GeV

2

Q

v

xu

v

xd 0.05) × xS ( 0.05) × xg (

H1 and ZEUS

0.2 0.4 0.6 0.8 1

HERA PDF 1.0

Uncertainties

experimental:

Δχ2=1

model:

Different set of values of fs, mc, mb, Q2

min, Q0 2

parameterization:

envelope of parameter variation e.g. Q0

2, negative

gluon, relax Bu=Bd, additional parameter.

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14

Relative Uncertainties at High Q2

At Q2 = 10000GeV2, 2% uncertainty on gluon for x<0.01.

0.2 0.4 0.6 0.8 1

2

=10000 GeV

2

Q

v

xu

0.2 0.4 0.6 0.8 1

0.2

0.2

4

10

3

10

2

10

1

10 1

x

0.2

0.2

0.2

0.2

0.2 0.4 0.6 0.8 1 0.2 0.4 0.6 0.8 1

2

=10000 GeV

2

Q

v

xd

HERAPDF1.0

exp. uncert.

model uncert. param uncert.

0.2 0.4 0.6 0.8 1

0.2

0.2

4

10

3

10

2

10

1

10 1

x

0.2

0.2

0.2

0.2

0.2 0.4 0.6 0.8 1 10 20 30 40 50

sea

xu

sea

xd

sea

xs

sea

xc

sea

xb

2

=10000 GeV

2

Q xS

10 20 30 40 50

0.2

0.2

4

10

3

10

2

10

1

10 1

x

0.2

0.2

0.2

0.2

10 20 30 40 50 20 40 60 80 100

2

=10000 GeV

2

Q xg

20 40 60 80 100

0.2

0.2

4

10

3

10

2

10

1

10 1

x

0.2

0.2

0.2

0.2

20 40 60 80 100

H1 and ZEUS

SLIDE 15

15 0 0.5 1 1.5 2 2.5 3 3.5 4 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

A(W) y

0 0.5 1 1.5 2 2.5 3 3.5 4 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

CDF data HERAPDF1.0 total uncert. MSTW08

0 0.5 1 1.5 2 2.5 3 3.5 4 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0 0.5 1 1.5 2 2.5 3 3.5 4 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0 0.5 1 1.5 2 2.5 3 3.5 4 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0 0.5 1 1.5 2 2.5 3 3.5 4 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

HERA PDF and Tevatron Data

Good description of Tevatron data by HERA PDF.

Tevatron Jet Cross Sections

2.0 < |yjet| < 2.4 (x 10-9) 1.6 < |yjet| < 2.0 (x 10-6) 1.2 < |yjet| < 1.6 (x 10-3) 0.8 < |yjet| < 1.2 0.4 < |yjet| < 0.8 (x 103) |yjet| < 0.4 (x 106)

D0 RunII

HERAPDF1.0

Cone R=0.7 - fastNLO

(+ non-perturbative corr.)

PT jet [Gev/c] d2σ/dyjetdpT jet [nb/(Gev/c)]

10

15

10

12

10

9

10

6

10

3

1 10 3 10 6 10 8 100 200 300 400 500 600 700

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16

HERA PDFs for LHC

Several predictions are calculated with reasonable uncertainties.

⏐ η ⏐ 0.5 1 1.5 2 Asymmetry 0.1 0.2 0.3 0.4 0.5 ⏐ η ⏐ 0.5 1 1.5 2 Asymmetry 0.1 0.2 0.3 0.4 0.5

=7 TeV) s Data 2010 ( MC NLO, CTEQ 6.6 MC NLO, HERAPDF 1.0 DYNNLO, MSTW 08

1

L dt = 315 nb

∫

ν e → W

ATLAS ⏐ η ⏐ 0.5 1 1.5 2 Asymmetry 0.1 0.2 0.3 0.4 0.5 ⏐ η ⏐ 0.5 1 1.5 2 Asymmetry 0.1 0.2 0.3 0.4 0.5

=7 TeV) s Data 2010 ( MC NLO, CTEQ 6.6 MC NLO, HERAPDF 1.0 DYNNLO, MSTW 08

1

L dt = 310 nb

∫

ν µ → W

ATLAS

CERN-PH-EP-2010-037 arXiv:hep-ex 1010.2130

Comparison with data has started.

PDF1.0 HERA TeV 7 = s

G. Watt, PDF4LHC, 2010

lepton

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Further measurements at HERA

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18

Further input from HERA

HERA PDF1.0 uses inclusive DIS cross section in HERA I only. HERA II High Q2 NC/CC cross sections – Increase of electron data NC: More sensitivity to xF3 i.e. valence quarks (u+d) – Increase of positron data CC: More sensitivity to d quark Inclusive Jet cross sections Longitudinal structure functions Heavy flavour structure functions 170pb-1 100pb-1 e+p 180pb-1 20pb-1 e-p HERA-II HERA-I

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19

HERA I+II NC cross sections

Improved precision. Clear separation of e+p and e-p at high Q2

H1 and ZEUS

HERA Structure Functions Working Group June 2010

x = 0.02 (x300.0) x = 0.032 (x170.0) x = 0.05 (x90.0) x = 0.08 (x50.0) x = 0.13 (x20.0) x = 0.18 (x8.0) x = 0.25 (x2.4) x = 0.40 (x0.7) x = 0.65

Q2/ GeV2 σr,NC(x,Q2)

HERA I+II NC e+p (prel.) HERA I+II NC e-p (prel.) HERAPDF1.0 e+p HERAPDF1.0 e-p

±

10

2

10

1

1 10 10 2 10 3 10

2

10

3

10

4

10

5

∑

− = ) (

3

q q x B xF

q

H1 and ZEUS

x = 0.02 (x300.0) x = 0.032 (x170.0) x = 0.05 (x90.0) x = 0.08 (x50.0) x = 0.13 (x20.0) x = 0.18 (x8.0) x = 0.25 (x2.4) x = 0.40 (x0.7) x = 0.65

Q2/ GeV2 σr,NC(x,Q2)

HERA I NC e+p HERA I NC e-p HERAPDF1.0 e+p HERAPDF1.0 e-p

± 10

2

10

1

1 10 10 2 10 3 10

2

10

3

10

4

10

5

to be included: ZEUS 06-07 e+p NC

valence quark HERA II NC are also combined.

H1 e+p, e-p
ZEUS e-p

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20

HERA I+II combined CC cross sections

Sensitive to valence quarks.

0.5 1 1.5 2 0.5 1 0.2 0.4 0.6 0.8

H1 and ZEUS

σr,CC(x,Q2)

Q2 = 300 GeV2

Q2 = 500 GeV2

Q2 = 1000 GeV2 Q2 = 1500 GeV2 Q2 = 2000 GeV2 Q2 = 3000 GeV2 10-2 10-1 Q2 = 5000 GeV2 10-2 10-1 Q2 = 8000 GeV2

x

HERA Inclusive Working Group June 2010

10-2 10-1 Q2 = 15000 GeV2 10-2 10-1 Q2 = 30000 GeV2

x

HERA I+II CC e-p (prel.) HERAPDF1.0

0.5 1 1.5 0.2 0.4 0.6 0.05 0.1 0.15

H1 and ZEUS

σr,CC(x,Q2)

Q2 = 300 GeV2

+

Q2 = 500 GeV2 Q2 = 1000 GeV2 Q2 = 1500 GeV2 Q2 = 2000 GeV2 Q2 = 3000 GeV2 10-2 10-1 Q2 = 5000 GeV2 10-2 10-1 Q2 = 8000 GeV2

x

HERA Structure Functions Working Group June 2010

10-2 10-1 Q2 = 15000 GeV2 10-2 10-1 Q2 = 30000 GeV2

x

HERA I+II CC e+p (prel.) HERAPDF1.0

[ ]

) ( ) 1 ( ) (

2

s d y c u p e

CC r

+ − + + ∝

+

σ

[ ]

) ( ) 1 ( ) (

2

s d y c u p e

CC r

+ − + + ∝

−

σ

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21

0.2 0.4 0.6 0.8 1

4

10

3

10

2

10

1

10 1 0.2 0.4 0.6 0.8 1 HERAPDF1.5 (prel.)

exp. uncert.

model uncert. parametrization uncert.

x xf

2

= 10 GeV

2

Q

v

xu

v

xd 0.05) × xS ( 0.05) × xg (

HERA Structure Functions Working Group July 2010

H1 and ZEUS HERA I+II Combined PDF Fit

0.2 0.4 0.6 0.8 1

HERA PDF 1.5 (prel.)

Uncertainties at the high x region reduced.

0.2 0.4 0.6 0.8 1

4

10

3

10

2

10

1

10 1 0.2 0.4 0.6 0.8 1 HERAPDF1.0

exp. uncert.

model uncert. parametrization uncert.

x xf

2

= 10 GeV

2

Q

v

xu

v

xd 0.05) × xS ( 0.05) × xg (

H1 and ZEUS HERA I Combined PDF Fit

0.2 0.4 0.6 0.8 1

Using HERA I+II combined data. Same setting as HERA PDF 1.0.

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22

Inclusive Jet measurements in HERA II

g

Directly sensitive to gluon density at medium x.

ZEUS

10

3

10

2

10

1

1 10 10 2 10 3 10 4 10 5 10 6 10 7 5 10 15 20 25 30 35 40 45

125 < Q2 < 250 GeV2 (x100000) 250 < Q2 < 500 GeV2 (x10000) 500 < Q2 < 1000 GeV2 (x1000) 1000 < Q2 < 2000 GeV2 (x100) 2000 < Q2 < 5000 GeV2 (x10) Q2 > 5000 GeV2 (x1)

ZEUS (prel.) 300 pb-1 NLO hadr Z0 ⊗ ⊗

2 < ηB

jet

< 1.5 |cos γh| < 0.65

jet energy scale uncertainty

Ejet

T,B

(GeV) dσ/dEjet

T,B

(pb/GeV)

ZEUS

102 10 1 10-1 10-2 10-3 ZEUS (prel.) 189 pb-1 NLO hadr: p/γ PDFs ⊗ (Klasen et al.) ZEUS-S/GRV-HO

MSTW08/GRV-HO ZEUS-S/AFG04 ZEUS-S/CJK E

jet1 T > 21 GeV, E jet2 T > 17 GeV

1 < η jet < 2.5

Q2 < 1 GeV2 0.2 < y < 0.85 jet energy scale uncertainty

dσ/dE

–– jet T (pb/GeV)

0.5

0.5 20 30 40 50 60 70 80

E

–– jet T (GeV)

rel. diff. to NLO

Also allows simultaneous constraints of PDFs and αS.

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23

Longitudinal structure function: FL

gluon emission in the proton FL≠0

i.e. FL directly reflects gluon dynamics in the proton.

⎥ ⎦ ⎤ ⎢ ⎣ ⎡ ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ − + =

∑ ∫

q q x s L

z zg z x e F z dz x F ) ( 1 8 3 16 4

2 2 1 3 2

π α

gluon PDF

In pQCD: Longitudinal photon cannot interact with a quark FL=0 Measurement of FL is good test for the current understanding of proton structure and QCD.

q q γ* < <

FL is proportional to the cross section of longitudinal photon

interacting with proton.

In naïve QPM, proton has co-linear spin ½ quarks only.

L L

F σ ∝

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24

Measurement of FL

Measured cross section is a combination of F2 and FL.
Separation of FL from F2.

HERA was successfully operated with low Ep for its last months. Data sets with three different energy are available. Direct FL measurements at low x (x: 10-4 ~10-3) = gluon dominance.

Extraction of structure functions without QCD assumption
Consistency check of pQCD framework for the proton structure.

) , ( ) , ( ) ( ~

2 2 2 2

Q x F Y y Q x F p e

L + ±

− = σ

At low Q2

2 1 ) 1 ( 1

2

< < → − + =

+ +

Y y Y

sx Q y

2

=

→ multiple beam energies Cross sections at the same (x, Q2) but the different y (Ep = 920, 575, 460 GeV) GeV 225 , 252 , 318 = s

SLIDE 25

25

Reduced cross sec. at Ep= 460,575,920GeV

The data covers 0.85 > y > 0.1 Difference at low-x (i.e. high-y) FL

0.8 1 1.2 1.4

σr

Q2=2.5GeV2 Q2=3.5GeV2 H1 and ZEUS Q2=5GeV2 Q2=6.5GeV2 Q2=8.5GeV2 Q2=12GeV2

0.75 1 1.25 1.5 1.75

σr

Q2=15GeV2 Q2=20GeV2 Q2=24GeV2 Q2=32GeV2 Q2=45GeV2 Q2=60GeV2

0.5 1 1.5

σr

Q2=80GeV2 Q2=110GeV2 Q2=150GeV2 Q2=200GeV2 Q2=250GeV2 Q2=300GeV2

0.25 0.5 0.75 1 1.25 10

4 10
2

σr x

Q2=400GeV2

10

4 10
2

x

Q2=500GeV2

10

4 10
2

x

Q2=650GeV2

10

4 10
2

x

Q2=800GeV2

HERA prel.

Ep=920 GeV Ep=575 GeV Ep=460 GeV

HERAPDF1.0

σr920 σr575 σr460

HERA Inclusive Workging Group March 2010

Note: ZEUS covers 24<Q2<110 GeV2. Still trying to go lower Q2

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26

FL extraction

At given (x, Q2) bin, FL should be seen as a negative slope.

1 1.2 1.4 1.6

X=0.00060

Q2=32 GeV2

σr(x,Q2,y)

X=0.00067 X=0.00074

H1 and ZEUS

1 1.2 1.4 1.6 0.5 1

X=0.00084

0.5 1

X=0.00097

0.5 1

X=0.00129

y2/(1+(1-y)2)

HERA prel.

Ep=920 GeV Ep=575 GeV Ep=460 GeV Linear fit

HERA Inclusive Workging Group March 2010

) , ( ) , ( ) ( ~

2 2 2 2

Q x F Y y Q x F p e

L + ±

− = σ

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27

HERA FL

FL, averaged over x, for each Q2 bin Good agreement between data and prediction for Q2>10 GeV2.

0.2

0.2 0.4 10 10

2

Q2 / GeV2 FL

0.000059 0.000087 0.000128 0.000168 0.000231 0.000324 0.000404 0.000534 0.000641 0.000855 0.001215 0.001599 0.002113 0.002927 0.003795 0.005420 0.006843 0.009109 0.012250 0.020170 0.026220 0.032270

x

HERA preliminary HERAPDF1.0

H1 and ZEUS

HERA Inclusive Workging Group March 2010

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28

Heavy Flavour production

Dominant process of heavy quark production:

Boson-Gluon-Fusion (BGF)

Two schemes to treat heavy quarks in pQCD;

– massive scheme (FFN) appropriate for Q2 ~ Mq

2

Heavy quarks are produced via BGF. Sensitive to gluon PDFs – massless scheme (ZMVFN) appropriate for Q2 >> Mq

2

Heavy quarks are massless and exist in the proton if Q2 is above the mass threshold. Intrinsic heavy quarks’ PDFs May affect on description of low Q2 FL.

0.2

0.2 0.4 10 10

2

Q2 / GeV2 FL

0.000059 0.000087 0.000128 0.000168 0.000231 0.000324 0.000404 0.000534 0.000641 0.000855 0.001215 0.001599 0.002113 0.002927 0.003795 0.005420 0.006843 0.009109 0.012250 0.020170 0.026220 0.032270

x

HERA preliminary

H1 and ZEUS

HERA Inclusive Working Group April 2010 ACOT full ACOT-χ RT optimized FFNS

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29

Charm mass impact on LHC W cross sec.

mc: 1.4 GeV 1.65 GeV. mc value in HERA PDF 1.0 does affect on LHC W cross section by ~ 3%. W+ cross section

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30

HERA combined F2

cc

F2

cc is extracted for large

kinematic region. – different methods

D mesons by slow

pions

Impact parameter

tagging

Muons from semi-

leptonic decay – different data sets

HERA I and II (partial)

Combination gives very precise data.

0.25 10

4

10

3

Q2=2GeV2

F2

cc _

10

4

10

3

Q2=4GeV2

10

4

10

3

Q2=6.5GeV2

October 2009

0.5 10

3

Q2=12 GeV2

10

3

10

2

Q2=20 GeV2

10

3

10

2

Q2=35 GeV2

HERA Heavy Flavour Working Group

0.5 10

3

10

2

Q2=60 GeV2

10

2

Q2=120GeV2

10

2

10

1

Q2=200GeV2

0.2 10

2

10

1

Q2=400GeV2

10

2

10

1

Q2=1000 GeV2

x

HERA (prel.) H1 D* HERA II (prel.) H1 D* HERA I H1 LTT HERA II (prel.) H1 LTT HERA I ZEUS µ 05 ZEUS D+ 05 ZEUS D0 05 ZEUS D* 99-00 ZEUS D* 96-97

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31

HERA F2

cc

Precision is 5-10%. Possible to constrain theory calculation. Better understanding

f charm treatment

and mc in QCD fits can be expected.

H1 and ZEUS

0.2

F2

cc _

Q2= 2 GeV2 Q2= 4 GeV2

October 2009

Q2= 6.5GeV2

0.5

Q2= 12GeV2 Q2= 20GeV2

HERA Heavy Flavour Working Group

Q2= 35GeV2

0.5

Q2= 60GeV2 Q2=120GeV2 Q2=200GeV2

0.5 10

4 10
3 10
2

Q2=400GeV2

10

4 10
3 10
2

x

Q2=1000GeV2 HERA (prel.) MSTW08 NNLO MSTW08 NLO CTEQ 6.6 GJR08 ABKM BMSN ABKM FFNS NLO ABKM FFNS NNLO

FFN FFN FFN

SLIDE 32

32

F2

bb

Methods:

– Impact parameter – tagging, μ+jet

Measurements are

consistent with each

ther.
Combination of

H1+ZEUS will provides improved precision

ZEUS

10 10

2

10

3

Q2 (GeV2) F2

bb _

+ 0.03 i 0.000 0.025 0.050 0.075 0.100 0.125 0.150 0.175 0.200 0.225 x=0.00013 i=7 x=0.0002 i=6 x=0.0005 i=5 x=0.0013 i=4 x=0.002 i=3 x=0.005 i=2 x=0.013 i=1 x=0.032 i=0

ZEUS (prel.) vtx 354 pb-1 ZEUS (prel.) e 363 pb-1 ZEUS µ 114 pb-1 ZEUS µ+vtx 126 pb-1 H1 vtx ZEUS-S+HVQDIS GJR08 NLO ABKM NNLO MSTW08 NLO MSTW08 NNLO CTEQ6.6 NLO

SLIDE 33

33

Summary

HERA results are valuable input for to understand the proton structure. Combination of H1 and ZEUS measurements provides very precise data. A very good PDF determination in HERA PDF1.0. Using the full HERA II statistics, the analyses of high-Q2 NC/CC, jets and heavy flavour processes will improve the precision of the results. Further understanding of the proton structure may come.

SLIDE 34

Backup

SLIDE 35

35

Input for HERA I combined data

SLIDE 36

36