fc measurements at hera 2€¦ · 2 @ hera ii on the way to precision measurement 0.4 0.2 10-5 10-3...
TRANSCRIPT
New trends in HERA Physics, Ringberg 2008
Katerina Lipka
Fc2 measurements at HERA
Charm production at HERA: why now?
HERA I : PDF – central measurement of HERA
• PDF obtained from the fits to inclusive F2
• Inclusive F2 experimentally very precise
• Contribution of events with charm to F2 high
• Measurement of Fc2 has large uncertainties
now: precise PDF – crucial importance for the LHC
• Combined HERA PDF are of unprecedented precision
• BUT dependent on parameterization of the QCD fit
• Need a cross check / direct access to the gluon
• Final state measurements (jets, heavy quarks) extremely important
• Fc2 @ HERA II on the way to precision measurement
0.4
0.2
10-5 10-3 x
HERA I Fc / F22
Q2 = 11 GeV2
K. Lipka Charm production and Fc2 at HERA 2
Dominated by Boson – Gluon Fusion (BGF)
• gluon directly involved:
include in a global PDF fit
important cross-check of the g(xg)
• charm mass – additional hard scale:
pQCD calculations possible;
multiple scales: calculations complicated
Charm production at HERA
Factorization:
σ(ep→D*X)=Proton Structure ⊗ Photon Structure ⊗ Matrix Element ⊗ Fragmentation
eγ
c
c
frag
men
tatio
n
hadr
ons
D*
to learn something about PDFs:
calculate hard ME, measure cross section, understand fragmentation
K. Lipka Charm production and Fc2 at HERA 3
Presented in this talk
Hard ME:
• NLO calculations and Monte-Carlo simulations
Charm tag methods and extraction of Fc2 :
• Charm tag via reconstruction of charmed mesons
• Extrapolation to the full phase space
• Fragmentation measurement
• Charm tag via track displacement measurement
Results and discussion
K. Lipka Charm production and Fc2 at HERA 4
Models of charm productionMassive calculation, fixed order QCD calculation, FFNS
• correct threshold suppression, no collinear divergences, terms ~log(μ/m)
• no factorization, no conceptual necessity fo FFs, no resummation
• valid for 0 ≤ pt2≤ mc
2, fixed order logarithms ln(pt2/mc
2) large for pt2>>mc
2
Models for charm at HERA: FMNR (Photoproduction), HVQDIS (DIS),
Massless calculation (ZM-VFNS)• large collinear ln (μ2/m2
c)-terms resummed in evolved PDFs and FFs (LL, NLL), good for large μ2~pt
2>>mc2
• universality of PDFs and FFs via factorization theorem, global analysis
• terms (mc/pt)n neglected in the hard part – breaks down @ threshold
Not appropriate for charm production at HERA (close to threshold)
Generalized mass calculation (GM-VFNS) → Hubert’s talkAvailable for charm production in γp at HERA, DIS is on the way
K. Lipka Charm production and Fc2 at HERA 5
RAPGAP• matrix element calculated in LO QCD
• higher order contributions via parton showers
• parton evolution in collinear approximation (DGLAP equations)
• charm is massive in BGF
CASCADE• gluon density unintegrated in gluon transverse momentum kT
• only gluons in proton
• higher order contributions via initial state parton showers
• based on CCFM equations
• charm is massive in BGF
Hadronization via Lund String model (Jetset)
Monte-Carlo models for data corrections
K. Lipka Charm production and Fc2 at HERA 6
π
πsK
e
Liquid ArCalorimeter
“Spaghetti” Calorimeter
central tracking detector
D*+→D0 πs+ → K-π+ πs
+ (+ c.c.)
Kinematics regimes:
DIS: 5 <Q2< 1000 GeV2
Photoproduction Q2< 2 GeV2
Charm tag via D*± production
) [GeV]π) - M(KππM(K0.14 0.15 0.16 0.17
Ent
ries
/ 0.5
MeV
2000
4000
6000
282±N(D*) = 20803
) [GeV]π) - M(KππM(K0.14 0.15 0.16 0.17
Ent
ries
/ 0.5
MeV
2000
4000
6000 slow±π ±π +Κ
fit
H1 Preliminary
HERA II
2 < 100 GeV25 < Q0.02 < y < 0.7
(D*)| < 1.5η| (D*) > 1.5 GeV
Tp
Electron reconstructed in
SpaCal: Q2<100 GeV2
LAr: Q2>100 GeV2
K. Lipka Charm production and Fc2 at HERA 7
(D*)η-1.5 -1 -0.5 0 0.5 1 1.5
(D*)
(n
b)
η/dσd
0
0.5
1
1.5
2
2.5
3
3.5
(D*)η-1.5 -1 -0.5 0 0.5 1 1.5
(D*)
(n
b)
η/dσd
0
0.5
1
1.5
2
2.5
3
3.5
e+D*+X→ep
-1ZEUS (prel.) 162 pb
HVQDIS
ZEUS
(D*)η-1.5 -1 -0.5 0 0.5 1 1.5
[n
b/G
eV]
T d
pη
/ d
σ2d
0
0.5
1
1.5
(D*)η-1.5 -1 -0.5 0 0.5 1 1.5
[n
b/G
eV]
T d
pη
/ d
σ2d
0
0.5
1
1.5
(D*) < 2.5 GeVT
1.5 < p
H1 PreliminaryHERA II
2 < 100 GeV25 < Q0.02 < y < 0.7
D* in DIS
(D*)η-1.5 -1 -0.5 0 0.5 1 1.5
[n
b/G
eV]
T d
pη
/ d
σ2d
0
0.5
1
(D*)η-1.5 -1 -0.5 0 0.5 1 1.5
[n
b/G
eV]
T d
pη
/ d
σ2d
0
0.5
1
(D*) < 3.5 GeVT
2.5 < p
H1 data (prel.)
HVQDIS (MRST2004FF3nlo)
HVQDIS (CTEQ5f3)
D* in DIS
(D*)η-1.5 -1 -0.5 0 0.5 1 1.5
[n
b/G
eV]
T d
pη
/ d
σ2d
0
0.1
0.2
0.3
0.4
(D*)η-1.5 -1 -0.5 0 0.5 1 1.5
[n
b/G
eV]
T d
pη
/ d
σ2d
0
0.1
0.2
0.3
0.4
(D*) < 5.5 GeVT
3.5 < p
< 1.6 GeVc1.3 < m2c + 4m2 = Q2
0μ
< 40
μ/f,r
μ1 <
0.4±(Kartvelishvili) = 3.3 α
D* in DIS
(D*)η-1.5 -1 -0.5 0 0.5 1 1.5
[n
b/G
eV]
T d
pη
/ d
σ2d
0
0.01
0.02
0.03
(D*)η-1.5 -1 -0.5 0 0.5 1 1.5
[n
b/G
eV]
T d
pη
/ d
σ2d
0
0.01
0.02
0.03
(D*) < 14.0 GeVT
5.5 < p
D* in DIS
D* production in DIS (5<Q2<100 GeV2)
H1: FFNs NLO does good job describing the D* kinematics,
but underestimates forward region ay low pT(D*)
ZEUS: no forward access in the data seen. Data precision will improve
K. Lipka Charm production and Fc2 at HERA 8
D* production in DIS (Q2>100 GeV2)
(D*)η-1 0 1
[p
b]
η/dσd
0
50
100
1502D* production at high Q
(D*)η-1 0 1
[p
b]
η/dσd
0
50
100
150
H1 data (prel.)
RAPGAP (CTEQ65m)
CASCADE (A0)
HVQDIS (MRST2004FF3nlo)
H1 Preliminary HERA II
2 < 1000 GeV2100 < Q0.02 < y < 0.7
(D*) > 1.5 GeVT
p
(D*) [GeV/c]T
p5 10 15 20
[p
b]
T/d
pσd
10
210
2D* production at high Q
(D*) [GeV/c]T
p5 10 15 20
[p
b]
T/d
pσd
10
210H1 data (prel.)
RAPGAP (CTEQ65m)
CASCADE (A0)
HVQDIS (MRST2004FF3nlo)
H1 Preliminary HERA II
2 < 1000 GeV2100 < Q0.02 < y < 0.7
(D*) | < 1.5η|
• D* production at high Q2: description by the LO Monte-Carlo gets worse
• NLO FFNs describes data very well
K. Lipka Charm production and Fc2 at HERA 9
D* production in DIS: Q2 slope
]2 [GeV2Q10 210 310
]2 [
pb
/GeV
2 /d
Qσd
-210
-110
1
10
210
310
D* production in DIS
H1 data (prel.)
RAPGAP (CTEQ65m)
RAPGAP (CTEQ6l)
CASCADE (A0)
H1 Preliminary HERA II
0.02 < y < 0.7 (D*) | < 1.5η| (D*) > 1.5 GeV
Tp
]2 [GeV2Q10 210 310
]2 [
pb
/GeV
2 /d
Qσd
-210
-110
1
10
210
310
Monte-Carlo models don’t describe the Q2 slope of the D* cross section
K. Lipka Charm production and Fc2 at HERA 10
D* production in DIS
]2 [GeV2Q10 210 310
]2 [
pb
/GeV
2 /d
Qσd
-210
-110
1
10
210
310
D* production in DIS
H1 data (prel.)
HVQDIS (MRST2004FF3nlo)
H1 Preliminary HERA II
0.02 < y < 0.7 (D*) | < 1.5η| (D*) > 1.5 GeV
Tp
]2 [GeV2Q10 210 310
]2 [
pb
/GeV
2 /d
Qσd
-210
-110
1
10
210
310
NLO FFNs calculation does good job (surprising, should break down for high Q2)
K. Lipka Charm production and Fc2 at HERA 11
ZEUS
10-5
10-4
10-3
10-2
10-1
1
10
10 2
10-1
1 10 102
103
Q2 (GeV2)
dσ/d
Q2
(nb/
GeV
2 )
ZEUS (prel.) 162 pb-1
ZEUS BPC (prel.) 98-00
ZEUS 98-00
HVQDIS
) 2 (GeV2Q10 210 310
)2 (
nb
/ G
eV2
/dQ
σd
-410
-310
-210
-110
1
10ZEUS
+ X0 e + D→ep
HERA I-1ZEUS 65 pb
HERA II-1ZEUS (prel.) 135 pbNLO + Fragmentation
) 2 (GeV2Q10 210 310
)2 (
nb
/ G
eV2
/dQ
σd
-410
-310
-210
-110
1
10
More to charmed meson production
K. Lipka Charm production and Fc2 at HERA 12
0Dη
-1.5 -1 -0.5 0 0.5 1 1.5
(n
b)
0D η
/dσd
0
0.5
1
1.5
2
2.5
3 + X0 e + D→ep
HERA II-1ZEUS (prel.) 135 pbNLO + Fragmentationbeauty contribution (RAPGAP)
0Dη
-1.5 -1 -0.5 0 0.5 1 1.5
(n
b)
0D η
/dσd
0
0.5
1
1.5
2
2.5
3ZEUS
±Dη-1.5 -1 -0.5 0 0.5 1 1.5
(n
b)
±D η
/dσd
0
0.2
0.4
0.6
0.8
1
1.2
1.4 + X± e + D→ep
HERA II-1ZEUS (prel.) 135 pbNLO + Fragmentationbeauty contribution (RAPGAP)
±Dη-1.5 -1 -0.5 0 0.5 1 1.5
(n
b)
±D η
/dσd
0
0.2
0.4
0.6
0.8
1
1.2
1.4ZEUS
D0
D+D0
• HERA-II, L=135pb-1
5<Q2<1000 GeV2 ,
pT(D)>3 GeV, Iη(D)I<1.6
• Lifetime information from the ZEUS Micro Vertex Detector used
• NLO FFNS describes data well
Visible cross section: pT(D*)>1.5 GeV, |η(D*)|<1.5
0.02<y<0.7, 5<Q2<1000 GeV2
Problem: detector sees only 30% of the phase space for c→D*
→ strong model dependence due to large extrapolation factors
Extrapolation problems:
1) Different extrapolation models
2) Unknown parameters within a single model:
mass of charm quark, scales,
fragmentation model → experimentally measurable: see next slides
)()(
(exp)(exp) 22 theoryFtheory
F cc
vis
viscc
σσ
=
Extraction of Fc2 from meson cross section
K. Lipka Charm production and Fc2 at HERA 13
Measurement of charm fragmentation in epMethods to reconstruct the energy of the parent quark:
Jet containing D*; problem: only small region of phase space accessible
• DIS: inclusive k⊥ algorithm applied in the γp frame, ET(D*-jet)>3 GeV
• significant contribution only from ŝ > 100 GeV² (much above threshold)
Hemisphere containing D*:
• experimental setup similar to e+e- , works at threshold, ŝ ≈ 4m²c
γp-system
cut:η>0
- take all particles towards γ
- project onto the plane ⊥ to the γ
- get Thrust axis
- Σ momenta of all particles in the D* hemisphere
⊥ γ direction
K. Lipka Charm production and Fc2 at HERA 14
Charm fragmentation in photoproduction
Parent quark approximated by a jet containing D*
• data: HERAI, L =120 pb-1, Q2<1GeV2;
• pT ( D*) >2 GeV, Iη(D∗)I<1.5
• inclusive k⊥ algorithm, ET(D*-jet)>9 GeV
K. Lipka Charm production and Fc2 at HERA 15
jet
DII
EPEz
2)( *+
=
• compared to the NLO FFNS (FMNR)
fragmentation model: Kartvelishvili
best fit α=2.67
)1()(* zzzDDc −∝ α
z
ZEUS
0
1
2
0.2 0.4 0.6 0.8 1z
1/σd
σ/dz ZEUS (120 pb-1)
FMNR×CPYThad(Kartvelishvili α=2.67
+0.25- 0.31)
FMNR×CPYThad(Kartvelishvili α=1.2)
FMNR×CPYThad(Kartvelishvili α=4.0)
Hemisphere method should include more final state gluon radiation than jet method
⇒ Measured distributions of the fragmentation variable should be different
⇒ Extracted parameters of the non-perturbativefragmentation function should agree
Data: H1 HERA I, L=75 pb-1 both methods used: ,
Differences between the methods:jet
DLjet pE
pEz)()( *
++
=hem
DLhem pE
pEz)()( *
++
=
• Measure in the common phase space: require presence of a D* jet
• Extract parameters for n.-p. FF using MC/ HVQDIS.
• Expect : parameters agree for different methods, different for MCs and HVQDIS
• Any differences at the threshold (absence of a D*-jet)?
Measurement of charm fragmentation in DIS
K. Lipka Charm production and Fc2 at HERA 16
Hemisphere method Jet methodRAPGAP MC: NLO (HVQDIS):
Fragmentation measurement: D*- Jet sample
• Distributions on hadron level look different (as expected)• MC (Rapgap) with standard n.p. FF yield reasonable description of data• Extracted n.p. FF parameters from zhem (α=4.5±0.6) and zjet (α=4.3±0.4) agree• HVQDIS ⊗ Kartvelishvili fragmentation: extracted parameters zhemi and zjet agree
Hemisphere method
K. Lipka Charm production and Fc2 at HERA 17
Fragmentation c → D*. No D*- jet sample
MC: Extracted parameters (α=10.3 ) inconsistent with jet-sample (α=4.5±0.6)HVQDIS: “no jet” (α=6.0 ) inconsistent with jet-sample (α=3.3±0.4)Fragmentation at threshold significantly harder than expected from the jet-sample
Treatment in extrapolation models: ŝ-dependent fragmentation
+ 1.7- 1.6
+ 1.0- 0.8
K. Lipka Charm production and Fc2 at HERA 18
Extrapolation Models in use:
• NLO: Riemersma et al: integrated form; HVQDIS: differential form,
fixed order massive calculation, Nf=3, FFNS, evolution: DGLAP
Parameters: PDFs: MRST04F3, mc = 1.43 GeV , μr=μf=μ=√ Q2+4mc2
Fragmentation: ŝ<70 GeV2: α =6.0, otherwise α=3.3
• CASCADE: massive LO ME + Parton showers,
proton structure: gluons only, evolution: CCFM
Parameters: PDFs: A0, mc = 1.43 GeV, μr=μf=μ=√ Q2+4mc2
Fragmentation: ŝ <70 GeV2; α = 8.2, otherwise α = 4.3
Back to extrapolation of σ(D*) to the Fc2
K. Lipka Charm production and Fc2 at HERA 19
ep → e D* X
0
100
200
Q4 d
2 σ/d
Q2 d
y [n
b G
eV2 ]
Q =2 7 GeV2 11GeV2 18GeV2
0
100
200 32GeV2 65GeV2 120GeV2
0
100
200 200GeV2
y10 -2 10 -1 10 -2 10 -1 1
440GeV2H1Preliminary
Data HERA-II
HVQDIS(MRST04FF3)total theoryuncertainty
fragmentationuncertainty
0
0
0 2 = 7 GeV2Q
0
0
0
0
0 211 GeV
0
0
0
0
0 218 GeV
0
0
0 232 GeV
0
0
0
0
0 265 GeV
0
0
0
0
0
0
0
0
0
02120 GeV
0
0
0
0
0
02200 GeV
0
0
0
0
0
0
0
0
0
02440 GeV
Data HERA II
CASCADE (A0)
H1 Preliminary
eD*X→ep
y
]2 [
nb
GeV
2/d
ydQ
σ 2 d4Q
1-1 10-2 10-1 10-210 0
100
200 0
100
200 0
100
200
Lowest y (highest x) overestimated by NLO, underestimated by CASCADE
D* cross sections vs NLO/CASCADE
K. Lipka Charm production and Fc2 at HERA 20
Extrapolation factors (σtot/σvis)
differ in NLO vs CASCADE:
3%-10% (low x) -100% (high x)
Differences in the models:
• LO+PS vs NLO
• Evolution
• Hadronization
Possible reason:
Hadronization
More studies have to be done
Ext
rap
ola
tio
n F
acto
r R
atio
CA
SC
AD
E/H
VQ
DIS
Q =2
0
1
2
3
7 GeV2 11 GeV2 18 GeV2
0
1
2
32 GeV2 65 GeV2 120 GeV2
0
1
2
200 GeV2 440 GeV2
x10 -5 10 -3 10 -5 10 -3 10 -1
Extrapolation factors NLO/CASCADE
K. Lipka Charm production and Fc2 at HERA 21
Results: Fc2 from D* measurement
2 = 7 GeV2Q
0
2
4
6
211 GeV
0
2
4
6
218 GeV
232 GeV
0
2
4
6
265 GeV
0
2
4
6
2120 GeV
2200 GeV
0
2
4
6
2440 GeV
GraphGraphGraph
< 1.6 GeVc1.3 < mμ < 2
rμ < μ0.5
D* HERA IICASCADE (A0)theoryuncertainty:
H1 Preliminary
in the CCFM scheme (CASCADE)cc2F
x
cc2F
-1 10-3 10-5 10-3 10-5 10 0
0.2
0.4
0
0.2
0.4
0
0.2
0.4
0.6Fcc
_
2 in the NLO DGLAP scheme (HVQDIS)
F2cc
–
Q =2
0
0.2
0.4
0.6
7 GeV2 11 GeV2 18 GeV2
0
0.2
0.4
32 GeV2 65 GeV2 120 GeV2
0
0.2
0.4
200 GeV2 440 GeV2
x10 -5 10 -3 10 -5 10 -3 10 -1
H1Preliminary
Data HERA-II
total theoryuncertainty
PDF variation
MRST04FF3CTEQ5F3
Experimental errors will further decrease – we are on the way to the final precision
K. Lipka Charm production and Fc2 at HERA 22
K. Lipka Charm production and Fc2 at HERA 23
Charm/beauty via other tag methods• Charm comes alone with beauty:
- More experimental details in Massimo’s talk
• Large mass : transverse momentum to Jet axis: muon ptrel
• Large lifetime: impact parameter δ, Significance S=δ/σ(δ)
• Semileptonic decays (e,μ)
• Different systematic uncertainties wrt. D-meson measurements
Jet
Jet
ptrel
μ
B+
B-
δ
/ cmδ-0.2 -0.15 -0.1 -0.05 0 0.05 0.1 0.15 0.2
Tra
cks
310
410
510
610
710
bb2 and Fcc
2Measurement of F
H1 PreliminaryH1 Data (Prel.)Total MCudscb
/ cmδ-0.2 -0.15 -0.1 -0.05 0 0.05 0.1 0.15 0.2
Tra
cks
310
410
510
610
710
0
10
10 2
10 3
0 1 2prel (GeV)
Mu
on
s
T (GeV)
ZEUS (prel.) HERA II 125 pb-1
MC sumcbuds
Charm in semileptonic events
K. Lipka Charm production and Fc2 at HERA 24
0
20
40
60
80
100
-1.5 -1 -0.5 0 0.5 1 1.5 2
ZEUS
ep→ eQQ–
X→ e μ X
ZEUS (prel.) HERA II 125 pb-1
Charm
Beauty
HVQDISHVQDIS
ημ
dσ/
dημ (
pb
)
Reasonable description
by the NLO FFNS
ZEUS
0
0.1
0.2
0.3
0.4
0.5
0.6
10-3
10-2
10-1
xF
2 cc_
Q2=30 GeV2
0
0.1
0.2
0.3
0.4
0.5
0.6
10-3
10-2
10-1
x
F2 cc_
Q2=130 GeV2
0
0.1
0.2
0.3
0.4
0.5
0.6
10-3
10-2
10-1
x
F2 cc_
Q2=1000 GeV2Charm
ZEUS (prel.) HERA II, 125 pb-1 (μ)ZEUS HERA I, 82 pb-1 (D*)H1 HERA I, 57 pb-1 (VTX)
ZEUS-S-FF mc=1.5, mb=4.75 GeVPDF uncertaintymc=1.3, mb=4.5 GeVmc=1.7, mb=5.0 GeV
Charm cross sections via lifetime tag vs D*H1 CHARM CROSS SECTION IN DIS
0
0.2
0.4
Q2= 6.5 GeV2σ∼cc_
Q2= 12 GeV2 Q2= 20 GeV2
0
0.2
0.4
Q2= 35 GeV2 Q2= 60 GeV2
10-4
10-3
10-2
Q2= 120 GeV2
x
0
0.2
0.4
10-4
10-3
10-2
Q2= 200 GeV2
H1 Preliminary
x10-4
10-3
10-2
Q2= 400 GeV2
x
H1 HERA IH1 HERA II (Prel.)H1 D✽ HERA II (Prel.)
K. Lipka Charm production and Fc2 at HERA 25
Charm cross sections vs VFNS (TR)
K. Lipka Charm production and Fc2 at HERA 26
H1 CHARM CROSS SECTION IN DIS
0
0.2
0.4
Q2= 6.5 GeV2σ∼cc_
Q2= 12 GeV2 Q2= 20 GeV2
0
0.2
0.4
Q2= 35 GeV2 Q2= 60 GeV2
10-4
10-3
10-2
Q2= 120 GeV2
x
0
0.2
0.4
10-4
10-3
10-2
Q2= 200 GeV2
H1 Preliminary
x10-4
10-3
10-2
Q2= 400 GeV2
x
H1 HERA IH1 HERA II (Prel.)
CTEQ6.6MSTW08 (Prel.)CCFM
Fc2 from lifetime tag vs MSTW NNLO
K. Lipka Charm production and Fc2 at HERA 27
H1 F2cc_(x,Q2)
10-1
1
10
10 2
10 3
10 4
10 5
10 102
103
x=0.0002, i=10
x=0.00032, i=9
x=0.0005, i=8
x=0.0008, i=7
x=0.0013, i=6
x=0.002, i=5
x=0.0032, i=4
x=0.005i=3
x=0.008i=2
x=0.013i=1
x=0.02i=0
H1 Preliminary
MSTW08 (Prel.)MSTW08 NNLO (Prel.)
H1 HERA II (Prel.)
Q2 / GeV2
F 2cc_ × 4
i
Recall Robert’s talk on Monday:
NNLO better fits the measured Fc2
Only Lifetime data of H1 are shown
Data will get better !
HERA measurement of Fc2
• Plenty of measurements
• Nice agreement between methods
• Experimental precision of several measurements will further improve
• Different methods will be combined: orthogonal errors!
• H1 and ZEUS results will be combined
• Sensitivity to the models (PDFs)
• Need proper (precise) theory
K. Lipka Charm production and Fc2 at HERA 28
10-1
1
10
10 2
10 3
10 4
10 5
10 6
10 7
10 8
10 9
10 10
10 11
1 10 102
103
Q2 (GeV2)
F2 cc–
HERA F2 cc–
H1 HERA I (D*)H1 HERA I (VTX)ZEUS HERA I (D*)ZEUS HERA I (D+, D0, Ds
+)ZEUS (prel.) HERA II:
D* D+ μH1 (prel.) HERA II:
D* VTX
NLO QCD:CTEQ5F3MRST2004FF3
x = 0.00003 (× 420)
x = 0.00005 (× 419)x = 0.00007
(× 418)x = 0.00013
(× 417)x = 0.00018 (× 416)
x = 0.0003 (× 415)
x = 0.00035 (× 414)
x = 0.0005 (× 413)
x = 0.0006 (× 412)
x = 0.0008 (× 411)
x = 0.001 (× 410)
x = 0.0012 (× 49)
x = 0.0015 (× 48)
x = 0.002 (× 47)
x = 0.003 (× 46)
x = 0.004 (× 45)
x = 0.006 (× 44)
x = 0.008 (× 43)x = 0.012
(× 42)
x = 0.02 (× 41)
x = 0.03(× 40)
Conclusions
Experimentally charm measurements at HERA get very precise:
We will get soon
• D* measurement at H1 on the way to 5% precision measurement
• D* measurements at ZEUS full HERA-II on the way
• Combination of different measurement methods
• Combination of H1 and ZEUS: cross calibration
• Enlarge the visible phase space (H1)
Extrapolation to the full phase space model dependent
Theory: massive NLO pQCD describes the data quite well
Model uncertainties larger than experimental errors
We still need:
• GMVFNS for DIS : proper charm treatment in the global fit
• NNLO
K. Lipka Charm production and Fc2 at HERA 29
0
0.2
0.4
F2 cc–
HERA F2 cc–
Q2 = 2 GeV2
H1 HERA I:D* VTX
ZEUS HERA II:D* D+, D0, Ds
+
H1 (prel.) HERA II:D* VTX
ZEUS (prel.) HERA II:D* D+ μ
NLO QCD:CTEQ5F3MRST2004FF3
4 GeV2 7 GeV2
0
0.2
0.4
11 GeV2 18 GeV2 30 GeV2
0
0.2
0.4
10-5
10-3
60 GeV2
10-5
10-3
130 GeV2
10-5
10-3
10-1
500 GeV2
x
Outlook:
Precision will improve
Results will be combined
0.4
0.2
10-5 10-3 x
HERA I Fc / F22
Q2 = 11 GeV2
Backup
D* in photoproduction (Q2 < 2 GeV2)
(D*)η-1.5 -1 -0.5 0 0.5 1 1.5
[nb
]η
eD
*X)/
d→
(ep
σd
10
20
30
40
(D*)η-1.5 -1 -0.5 0 0.5 1 1.5
[nb
]η
eD
*X)/
d→
(ep
σd
10
20
30
40H1 data (prel.)
FFNS (CTEQ5F3) < 1.7 GeV c1.3 < m
< 22
t+p2
cm / r,f
μ0.5 <
GMVFNS (CTEQ6.5)
H1 PreliminaryHERA II
D* in Photoproduction
(D*)η-1.5 -1 -0.5 0 0.5 1 1.5
[nb
]η
eD
*X)/
d→
(ep
σd
10
20
30
40
(D*)[GeV]t
p2 4 6 8 10 12
[nb
/GeV
]t
eD
*X)/
dp
→(e
p
σd
-210
-110
1
10
210H1 data (prel.)
FFNS (CTEQ5F3) < 1.7 GeV c1.3 < m
< 22
t+p2
cm / r,f
μ0.5 <
GMVFNS (CTEQ6.5)
H1 PreliminaryHERA II
D* in Photoproduction
2 < 2 GeV2Q < 285 GeV Pγ100 < W
(D*) > 1.8 GeVt
p
(D*)| < 1.5η|
(D*)[GeV]t
p2 4 6 8 10 12
[nb
/GeV
]t
eD
*X)/
dp
→(e
p
σd
-210
-110
1
10
210
[GeV] pγW100 150 200 250
[nb
/GeV
] pγ
eD
*X)/
dW
→(e
p
σd
0.2
0.4
0.6
0.8
[GeV] pγW100 150 200 250
[nb
/GeV
] pγ
eD
*X)/
dW
→(e
p
σd
0.2
0.4
0.6
0.8H1 data (prel.)
FFNS (CTEQ5F3) < 1.7 GeV c1.3 < m
< 22
t+p2
cm / r,f
μ0.5 <
GMVFNS (CTEQ6.5)
H1 PreliminaryHERA II
D* in Photoproduction
[GeV] pγW100 150 200 250
[nb
/GeV
] pγ
eD
*X)/
dW
→(e
p
σd
0.2
0.4
0.6
0.8• Measurement in the visible range:
PT(D*)>1.8 GeV, Iη(D*)I<1.5
Q2 < 2 GeV2, 0.1<y<0.8
• Good agreement with both NLO
• Large model uncertainties due to variation of the scales
K. Lipka Charm production and Fc2 at HERA 8
D* in photoproduction
(D*)η-1.5 -1 -0.5 0 0.5 1 1.5
(D
*)[n
b/G
eV]
ηd t
/dp
σ2
d
0
10
20
30
(D*)η-1.5 -1 -0.5 0 0.5 1 1.5
(D
*)[n
b/G
eV]
ηd t
/dp
σ2
d
0
10
20
30H1 PreliminaryHERA II (D*) < 2.5 GeV
t1.8 < p
D* in Photoproduction
(D*)η-1.5 -1 -0.5 0 0.5 1 1.5
(D
*)[n
b/G
eV]
ηd t
/dp
σ2
d
0
2
4
6
8
10
(D*)η-1.5 -1 -0.5 0 0.5 1 1.5
(D
*)[n
b/G
eV]
ηd t
/dp
σ2
d
0
2
4
6
8
10H1 PreliminaryHERA II (D*) < 4.5 GeV
t2.5 < p
D* in Photoproduction
(D*)η-1.5 -1 -0.5 0 0.5 1 1.5
(D
*)[n
b/G
eV]
ηd t
/dp
σ2
d
0
0.1
0.2
0.3
0.4
0.5
(D*)η-1.5 -1 -0.5 0 0.5 1 1.5
(D
*)[n
b/G
eV]
ηd t
/dp
σ2
d
0
0.1
0.2
0.3
0.4
0.5H1 PreliminaryHERA II (D*) < 12.5 GeV
t4.5 < p
D* in Photoproduction
H1 data (prel.)
FFNS (CTEQ5F3) < 1.7 GeV c1.3 < m
< 22t
+p2cm /
r,fμ0.5 <
GMVFNS (CTEQ6.5)
GM VFNS underestimates the forward region at high pT
K. Lipka Charm production and Fc2 at HERA 9