fc measurements at hera 2€¦ · 2 @ hera ii on the way to precision measurement 0.4 0.2 10-5 10-3...
TRANSCRIPT
![Page 1: Fc measurements at HERA 2€¦ · 2 @ HERA II on the way to precision measurement 0.4 0.2 10-5 10-3 x HERA I Fc / F 2 2 Q2 = 11 GeV2 K. Lipka Charm production and Fc 2 at HERA 2](https://reader036.vdocuments.net/reader036/viewer/2022081408/6059acc5339a5e68382ed855/html5/thumbnails/1.jpg)
New trends in HERA Physics, Ringberg 2008
Katerina Lipka
Fc2 measurements at HERA
![Page 2: Fc measurements at HERA 2€¦ · 2 @ HERA II on the way to precision measurement 0.4 0.2 10-5 10-3 x HERA I Fc / F 2 2 Q2 = 11 GeV2 K. Lipka Charm production and Fc 2 at HERA 2](https://reader036.vdocuments.net/reader036/viewer/2022081408/6059acc5339a5e68382ed855/html5/thumbnails/2.jpg)
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
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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
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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
![Page 5: Fc measurements at HERA 2€¦ · 2 @ HERA II on the way to precision measurement 0.4 0.2 10-5 10-3 x HERA I Fc / F 2 2 Q2 = 11 GeV2 K. Lipka Charm production and Fc 2 at HERA 2](https://reader036.vdocuments.net/reader036/viewer/2022081408/6059acc5339a5e68382ed855/html5/thumbnails/5.jpg)
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
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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
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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
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(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
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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
![Page 10: Fc measurements at HERA 2€¦ · 2 @ HERA II on the way to precision measurement 0.4 0.2 10-5 10-3 x HERA I Fc / F 2 2 Q2 = 11 GeV2 K. Lipka Charm production and Fc 2 at HERA 2](https://reader036.vdocuments.net/reader036/viewer/2022081408/6059acc5339a5e68382ed855/html5/thumbnails/10.jpg)
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
![Page 11: Fc measurements at HERA 2€¦ · 2 @ HERA II on the way to precision measurement 0.4 0.2 10-5 10-3 x HERA I Fc / F 2 2 Q2 = 11 GeV2 K. Lipka Charm production and Fc 2 at HERA 2](https://reader036.vdocuments.net/reader036/viewer/2022081408/6059acc5339a5e68382ed855/html5/thumbnails/11.jpg)
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
![Page 12: Fc measurements at HERA 2€¦ · 2 @ HERA II on the way to precision measurement 0.4 0.2 10-5 10-3 x HERA I Fc / F 2 2 Q2 = 11 GeV2 K. Lipka Charm production and Fc 2 at HERA 2](https://reader036.vdocuments.net/reader036/viewer/2022081408/6059acc5339a5e68382ed855/html5/thumbnails/12.jpg)
) 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
![Page 13: Fc measurements at HERA 2€¦ · 2 @ HERA II on the way to precision measurement 0.4 0.2 10-5 10-3 x HERA I Fc / F 2 2 Q2 = 11 GeV2 K. Lipka Charm production and Fc 2 at HERA 2](https://reader036.vdocuments.net/reader036/viewer/2022081408/6059acc5339a5e68382ed855/html5/thumbnails/13.jpg)
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
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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
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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)
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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 !
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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)
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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
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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
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Backup
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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
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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