The Legacy of HERAlevonian/papers/Prague_2013.pdf · Sergey Levonian DESY, Hamburg The Legacy of...
Transcript of The Legacy of HERAlevonian/papers/Prague_2013.pdf · Sergey Levonian DESY, Hamburg The Legacy of...
Sergey Levonian
DESY, Hamburg
The Legacy of HERA
Seminar of the Physics Institute of the Czech Academy of Sciencies Prague, 12-Feb-2013
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2
Looking deeper inside matter
λ = h/p ∼ 1E
Illustration of improved understandingof the structure of matter with time(and with increasing resolution power)
High energy scattering processhas been the basic tool during last 100 years
2
Looking deeper inside matter
λ = h/p ∼ 1E
Rutherford (1911)
– elastic (Coulomb) scattering of 7 MeV α on Au
– planetary model of atom ⇒ QM
; N(θ)∼ 1sin4(θ/2)
2
Looking deeper inside matter
λ = h/p ∼ 1E
Rutherford (1911)
– elastic (Coulomb) scattering of 7 MeV α on Au
– planetary model of atom ⇒ QM
Hofstadter (1953)
– (in)elastic eN scattering of 400 MeV electrons
– Nucleus structure; size of A,p
2
Looking deeper inside matter
λ = h/p ∼ 1E
Rutherford (1911)
– elastic (Coulomb) scattering of 7 MeV α on Au
– planetary model of atom ⇒ QM
Hofstadter (1953)
– (in)elastic eN scattering of 400 MeV electrons
– Nucleus structure; size of A,p
SLAC (1968)– Fixed target DIS with 20 GeV electron beam
– internal structure of hadrons
– experimental evidence for quarks
2
Looking deeper inside matter
λ = h/p ∼ 1E
Rutherford (1911)
– elastic (Coulomb) scattering of 7 MeV α on Au
– planetary model of atom ⇒ QM
Hofstadter (1953)
– (in)elastic eN scattering of 400 MeV electrons
– Nucleus structure; size of A,p
SLAC (1968)– Fixed target DIS with 20 GeV electron beam
– internal structure of hadrons
– experimental evidence for quarks
HERA (1992 − 2007)
– first (and so far the only) ep collider
– energy frontier:√s = 319 GeV
– resolution power down to 10−18m
– QCD in low x regime (x > 10−5)
2
Looking deeper inside matter
λ = h/p ∼ 1E
Rutherford (1911)
– elastic (Coulomb) scattering of 7 MeV α on Au
– planetary model of atom ⇒ QM
Hofstadter (1953)
– (in)elastic eN scattering of 400 MeV electrons
– Nucleus structure; size of A,p
SLAC (1968)– Fixed target DIS with 20 GeV electron beam
– internal structure of hadrons
– experimental evidence for quarks
HERA (1992 − 2007)
– first (and so far the only) ep collider
– energy frontier:√s = 319 GeV
– resolution power down to 10−18m
– QCD in low x regime (x > 10−5)
By increasing E we are not only looking deeper into matter,but also perform ‘backward evolution’ of the Universe in attemptto understand better fundamental forces of nature
2
Looking deeper inside matter Restoring Universe Evolution
→ 1µsec
HERATevatronLHC
λ = h/p ∼ 1E
E ∼ T
In the beginning the was the Idea...
e
p
1979
...then a lot of Hard Work...
e
p
1979
1984-1991
...then a lot of Hard Work...
e
p
1979
1984-19911986-1992
...then a lot of Hard Work...
e
p
Days of running
H1
Inte
grat
ed L
umin
osity
/ p
b-1
Status: 1-July-2007
0 500 1000 15000
100
200
300
400electronspositronslow E
HERA-1
HERA-2
1979
1984-19911986-1992
1992-2007
...and finally...
3
10 10
-7
-5
-3
-1
10
]2 [p
b/G
eV2
/dQ
σd
-710
-510
-310
-110
10
]2 [GeV2Q310 410
p CC (prel.)+H1 e
p CC (prel.)-H1 e
p CC 06-07 +ZEUS e
p CC 04-06-ZEUS e
p CC (HERAPDF 1.0)+SM e
p CC (HERAPDF 1.0)-SM e
p NC (prel.)+H1 ep NC (prel.)-H1 e
p NC 06-07 (prel.)+ZEUS ep NC 05-06-ZEUS e
p NC (HERAPDF 1.0)+SM ep NC (HERAPDF 1.0)-SM e
y < 0.9 = 0eP
HERA
0.2
0.4
0.6
0.8
1
-410 -310 -210 -110 1
0.2
0.4
0.6
0.8
1
HERAPDF1.5 (prel.)
exp. uncert.
model uncert.
parametrization uncert.
xxf 2 = 10 GeV2Q
vxu
vxd
0.05)×xS (
0.05)×xg (
HE
RA
Str
uctu
re F
unct
ions
Wor
king
Gro
upJu
ly 2
010
H1 and ZEUS HERA I+II Combined PDF Fit
0.2
0.4
0.6
0.8
1
)Z
(Msα0.11 0.12 0.13
)Z
(Msα0.11 0.12 0.13
uncertainty
exp.
th.
World averageS. Bethke, Eur. Phys. J. C64, 689 (2009)
D0 incl. midpoint cone jetsPhys. Rev. D80, 111107 (2009)
Aleph Event Shapes, NNLO+NLLAJHEP 08, 036 (2009)
Aleph 3−jet rate, NNLOPhys. Rev. Lett. 104, 072002 (2010)
jets, NLOTZEUS incl. anti−kPhys. Lett. B691, 127 (2010)
jets, NLOTZEUS incl. kPhys. Lett. B 649, 12 (2007)
multijets, NLOT k2H1 low QEur. Phys. J. C67, 1 (2010)
multijets, NLOT norm. k2H1 high QEur. Phys. J. C65, 363 (2010)
H1+ZEUS NC, CC and jet QCD fits, NLOH1−prelim−11−034
trijet, NLO2H1 high QH1−prelim−11−032
dijet, NLO2H1 high QH1−prelim−11−032
inclusive jet, NLO2H1 high QH1−prelim−11−032
[GeV]LQM200 400 600 800 1000
-210
-110
1
λH1 Search for First Generation Scalar Leptoquarks
H1d)+ (eL
1/2S~
H1 limitH1 94-00 limitH1 CI analysis limitCMS pair productionATLAS pair productionDØ pair productionOPAL indirect limit
HERA
Lots of Textbook results
-0.2
0
0.2
0.4
2 10 50
0.28
0.43
0.59
0.88
1.29
1.69
2.24
3.19
4.02
5.40
6.86
10.3
14.6
x 10
4
H1
ZEUS
HERAPDF1.0 NLOCT10 NLO JR09 NNLO
ABKM09 NNLONNPDF2.1 NLO
MSTW08 NNLO
H1 Collaboration
Q2 / GeV2
FL
HERAρ ZEUS 96-00ρ ZEUS 94
ρ ZEUS LPS 94ρ ZEUS 95ρ H1 95-96φ ZEUS 98-00φ ZEUS 94J/ψ ZEUS 98-00J/ψ ZEUS 96-97J/ψ H1 96-00
DVCS H1 HERA IDVCS H1 HERA II e-p
DVCS ZEUS LPS (31 pb -1)
Q2+M2(GeV2)
b(G
eV-2
)
0
2
4
6
8
10
12
14
0 10 20 30 40 50
HERA
10-1
1
10
10 2
10 3
0 5 10 15 20 25 30
H1 99-00 b jetH1 99-00 b→µ jetZEUS 96-00 b→µ jetZEUS 05 b→µ jetH1 (prel) 06/07 b →µ jetZEUS 96-97 b→eZEUS 120 pb -1 b→eH1 97-00 b→D*µZEUS 96-00 b→D*µZEUS 114 pb -1 bb→µµZEUS (prel) 128 pb -1 b jet
NLO QCD (FMNR)µ2 = 1/4 (m2 + pT
2)
µ2 = m2 + pT2
<pTb> (GeV)
dσ
/dp
Tb (
pb
/Ge
V)
dσ/dpT(ep→ebX)dσ/dpb
Q2<1GeV2, 0.2<y<0.8, |ηb|< 2
HERA
4 HERA: The World’s Only ep Collider
Days of running
H1
Inte
grat
ed L
umin
osity
/ p
b-1
Status: 1-July-2007
0 500 1000 15000
100
200
300
400electronspositronslow E
HERA-1
HERA-2
• 1998 Ep upgrade: 820 ⇒ 920 GeV(√s : 301 ⇒ 319 GeV)
• 2001 HERA-2 upgrade: L × 3, Polarised e+/e−
(〈P 〉 = 40%)
HERA-1 (1993-2000) ≃ 120 pb−1
HERA-2 (2003-2007) ≃ 380 pb−1
Final Data samples
H1+ZEUS: 2 × 0.5 fb−1
5 Deep-Inelastic Scattering at HERA
Neutral Current DIS: ep → e′X
Charged Current DIS: ep → νX
x
Q2
Kinematics: (Momentum transfer)2: Q2 = −q2
Bjorken x: x = Q2/(2p · q)
Inelasticity: y = (p · q)/(p · l)
(Total hadronic energy)2: W 2 = (p + q)2
W 2 ≃ Q2/x
(l)
(l)
(p)
(p)
6 Physics landscape at HERA
• HERA as Super-microscope
⊲ Proton structure at high resolution
⊲ Impact for LHC
• HERA as Energy frontier machine
⊲ Electroweak unification at work
⊲ Anything beyond the Standard Model?
• HERA as QCD laboratory
⊲ Putting QCD in stringent tests with:◦ Jets (parton evolution schemes, NLO QCD, αs)◦ Heavy flavor sector (multiscale problem: Q2,MQ, Et)◦ Diffraction (interplay of soft and hard physics)
⊲ HERA specifics: lox x physics
6 Physics landscape at HERA
• HERA as Super-microscope
⊲ Proton structure at high resolution
⊲ Impact for LHC
• HERA as Energy frontier machine
⊲ Electroweak unification at work
⊲ Anything beyond the Standard Model?
• HERA as QCD laboratory
⊲ Putting QCD in stringent tests with:◦ Jets (parton evolution schemes, NLO QCD, αs)◦ Heavy flavor sector (multiscale problem: Q2,MQ, Et)◦ Diffraction (interplay of soft and hard physics)
⊲ HERA specifics: lox x physics
e
q
e
q
⇒⇓
⇑
HERA
LEP
TEVATRON
LHC
6 Physics landscape at HERA
• HERA as Super-microscope
⊲ Proton structure at high resolution
⊲ Impact for LHC
• HERA as Energy frontier machine
⊲ Electroweak unification at work
⊲ Anything beyond the Standard Model?
• HERA as QCD laboratory
⊲ Putting QCD in stringent tests with:◦ Jets (parton evolution schemes, NLO QCD, αs)◦ Heavy flavor sector (multiscale problem: Q2,MQ, Et)◦ Diffraction (interplay of soft and hard physics)
⊲ HERA specifics: lox x physics
e
q
e
q
⇒⇓
⇑
HERA
LEP
TEVATRON
LHC
e+
p
e+
γ*
q
q
Q2
x
x0, k ⊥ 0
x i, k ⊥ i
x i+1 , k ⊥ i+1
6 Physics landscape at HERA
• HERA as Super-microscope
⊲ Proton structure at high resolution
⊲ Impact for LHC
• HERA as Energy frontier machine
⊲ Electroweak unification at work
⊲ Anything beyond the Standard Model?
• HERA as QCD laboratory
⊲ Putting QCD in stringent tests with:◦ Jets (parton evolution schemes, NLO QCD, αs)◦ Heavy flavor sector (multiscale problem: Q2,MQ, Et)◦ Diffraction (interplay of soft and hard physics)
⊲ HERA specifics: lox x physics
e
q
e
q
⇒⇓
⇑
HERA
LEP
TEVATRON
LHC
e+
p
e+
γ*
q
q
Q2
x
x0, k ⊥ 0
x i, k ⊥ i
x i+1 , k ⊥ i+1
Search for Novel PhenomenaPrecision Measurements
HERA as Energy Frontier Machine
7 HERA at Energy Frontier
.
Unpolarized DIS cross sections σCCpol (e
±p) = (1 ± Pe) · σCCunpol(e
±p)
3
10 10
-7
-5
-3
-1
10
]2 [p
b/G
eV2
/dQ
σd
-710
-510
-310
-110
10
]2 [GeV2Q310 410
p CC (prel.)+H1 e
p CC (prel.)-H1 e
p CC 06-07 +ZEUS e
p CC 04-06-ZEUS e
p CC (HERAPDF 1.0)+SM e
p CC (HERAPDF 1.0)-SM e
p NC (prel.)+H1 ep NC (prel.)-H1 e
p NC 06-07 (prel.)+ZEUS ep NC 05-06-ZEUS e
p NC (HERAPDF 1.0)+SM ep NC (HERAPDF 1.0)-SM e
y < 0.9 = 0eP
HERA
NC
CC
Electro-Weak Unification
7 HERA at Energy Frontier
.
Unpolarized DIS cross sections σCCpol (e
±p) = (1 ± Pe) · σCCunpol(e
±p)
3
10 10
-7
-5
-3
-1
10
]2 [p
b/G
eV2
/dQ
σd
-710
-510
-310
-110
10
]2 [GeV2Q310 410
p CC (prel.)+H1 e
p CC (prel.)-H1 e
p CC 06-07 +ZEUS e
p CC 04-06-ZEUS e
p CC (HERAPDF 1.0)+SM e
p CC (HERAPDF 1.0)-SM e
p NC (prel.)+H1 ep NC (prel.)-H1 e
p NC 06-07 (prel.)+ZEUS ep NC 05-06-ZEUS e
p NC (HERAPDF 1.0)+SM ep NC (HERAPDF 1.0)-SM e
y < 0.9 = 0eP
HERA
eP-1 -0.5 0 0.5 1
[pb]
CC
σ0
20
40
60
80
100
120p Scattering±HERA Charged Current e
2 > 400 GeV2Q
y < 0.9
Xν →p +e
Xν →p -e
HERAPDF 1.0
H1 HERA IH1 HERA II (prel.)ZEUS 98-06
H1 HERA IH1 HERA II (prel.)ZEUS 06-07ZEUS HERA I
eP-1 -0.5 0 0.5 1
[pb]
CC
σ0
20
40
60
80
100
120NC
CC
Electro-Weak UnificationNo W coupling
to e−R and e+L
8 Anything beyond the SM ?
e
q
e
q
⇒⇓
⇑
HERA
LEP
TEVATRON
√s = 319 GeV
LHC
So far all NC and CC HERA data were in good agreement with the SM.Try to look more carefully at the tails, using two strategies:
1. Specific BSM signals search (LQ, LFV, SUSY, ...) – guided by theory
2. Model independent generic search (data vs SM) – guided by data
9 Leptoquarks ?
e+
Proton(P)
γ,Z (W+)
e+ (ν)
q (q ,)
q
(a)
e+
q i
LQ
l+n
q k
λ n kλ 1 i
(b)
e+ l+n
LQ
q k– q i
–λ n k
λ 1 i
(c)
Q2e (GeV2)
even
ts /
bin
H1
(a)
Q2e (GeV2)
data
/ SM H1 (b)
1
10
10 2
5000 10000 15000 20000 25000 30000
1
10
5000 10000 15000 20000 25000 30000
Q2 = 16950 GeV2; y = 0:44; M = 196 GeVe+ jet� �
Et/GeV1994-97: High Q2 events.Rate in excess of Standard Model!
9 Leptoquarks ?
e+
Proton(P)
γ,Z (W+)
e+ (ν)
q (q ,)
q
(a)
e+
q i
LQ
l+n
q k
λ n kλ 1 i
(b)
e+ l+n
LQ
q k– q i
–λ n k
λ 1 i
(c)
Q2e (GeV2)
even
ts /
bin
H1
(a)
Q2e (GeV2)
data
/ SM H1 (b)
1
10
10 2
5000 10000 15000 20000 25000 30000
1
10
5000 10000 15000 20000 25000 30000
Q2 = 16950 GeV2; y = 0:44; M = 196 GeVe+ jet� �
Et/GeV1994-97: High Q2 events.Rate in excess of Standard Model!
2011: Final status
100 200 300
Eve
nts
/ GeV
-210
-110
1
10
210
310NC data
SM NC
CC data
SM CC
H1 p-e-1= 164 pb
[GeV]LQM100 200 300
Eve
nts
/ GeV
-210
-110
1
10
210
310NC data
SM NC
CC data
SM CC
H1 p+e-1= 282 pb
[GeV]LQM
H1 Search for First Generation Leptoquarks
L L
[GeV]LQM200 400 600 800 1000
-210
-110
1
λH1 Search for First Generation Scalar Leptoquarks
H1d)+ (eL
1/2S~
H1 limitH1 94-00 limitH1 CI analysis limitCMS pair productionATLAS pair productionDØ pair productionOPAL indirect limit
10 Model independent search for New Phenomena
j-je-j
-jµ-jννe-
e-eµe-µ-µ-jγ
-eγµ-γν-γγ-γ
j-j-je-j-j
-j-jµ-j-jν
e-e-jνe-e-
e-e-e-jµ-µµ-µe-ν-µ-µ-jµe--jνe--jν-µν-µe-
-j-jγ-e-jγ
-jν-γe-j-j-j
-j-j-jν-j-jν-γ-j-jνe--j-j-eγ
-jνe-e--jν-µe-
j-j-j-je-j-j-j-j
-j-j-j-jνj-j-j-j-j
j-je-j
-jµ-jννe-
e-eµe-µ-µ-jγ
-eγµ-γν-γγ-γ
j-j-je-j-j
-j-jµ-j-jν
e-e-jνe-e-
e-e-e-jµ-µµ-µe-ν-µ-µ-jµe--jνe--jν-µν-µe-
-j-jγ-e-jγ
-jν-γe-j-j-j
-j-j-jν-j-jν-γ-j-jνe--j-j-eγ
-jνe-e--jν-µe-
j-j-j-je-j-j-j-j
-j-j-j-jνj-j-j-j-j
j-je-j
-jµ-jννe-
e-eµe-µ-µ-jγ
-eγµ-γν-γγ-γ
j-j-je-j-j
-j-jµ-j-jν
e-e-jνe-e-
e-e-e-jµ-µµ-µe-ν-µ-µ-jµe--jνe--jν-µν-µe-
-j-jγ-e-jγ
-jν-γe-j-j-j
-j-j-jν-j-jν-γ-j-jνe--j-j-eγ
-jνe-e--jν-µe-
j-j-j-je-j-j-j-j
-j-j-j-jνj-j-j-j-j
SM
H1 Data
-210 -110 1 10 210 310 410 510
)-1p, 285 pb+H1 General Search at HERA (e
Events
H1
e+p
• Identify isolated objects:e, µ, γ, j, ν
• Select events, having at least twoobjects with high PT>20GeV
• Classify into exclusive channelscontaining from 2 to 5 objects
• Compare with SM predictions⇒ good overall agreement
• Find interesting regionswith greatest deviations from SMin kin. distributions (Mall, ΣPT )
⇒ Combine H1 and ZEUS data
10 Model independent search for New Phenomena
j-je-j
-jµ-jννe-
e-eµe-µ-µ-jγ
-eγµ-γν-γγ-γ
j-j-je-j-j
-j-jµ-j-jν
e-e-jνe-e-
e-e-e-jµ-µµ-µe-ν-µ-µ-jµe--jνe--jν-µν-µe-
-j-jγ-e-jγ
-jν-γe-j-j-j
-j-j-jν-j-jν-γ-j-jνe--j-j-eγ
-jνe-e--jν-µe-
j-j-j-je-j-j-j-j
-j-j-j-jνj-j-j-j-j
j-je-j
-jµ-jννe-
e-eµe-µ-µ-jγ
-eγµ-γν-γγ-γ
j-j-je-j-j
-j-jµ-j-jν
e-e-jνe-e-
e-e-e-jµ-µµ-µe-ν-µ-µ-jµe--jνe--jν-µν-µe-
-j-jγ-e-jγ
-jν-γe-j-j-j
-j-j-jν-j-jν-γ-j-jνe--j-j-eγ
-jνe-e--jν-µe-
j-j-j-je-j-j-j-j
-j-j-j-jνj-j-j-j-j
j-je-j
-jµ-jννe-
e-eµe-µ-µ-jγ
-eγµ-γν-γγ-γ
j-j-je-j-j
-j-jµ-j-jν
e-e-jνe-e-
e-e-e-jµ-µµ-µe-ν-µ-µ-jµe--jνe--jν-µν-µe-
-j-jγ-e-jγ
-jν-γe-j-j-j
-j-j-jν-j-jν-γ-j-jνe--j-j-eγ
-jνe-e--jν-µe-
j-j-j-je-j-j-j-j
-j-j-j-jνj-j-j-j-j
SM
H1 Data
-210 -110 1 10 210 310 410 510
)-1p, 285 pb+H1 General Search at HERA (e
Events
H1
[GeV]T PΣ0 20 40 60 80 100 120 140 160 180
Eve
nts
-210
-110
1
10
210
310
[GeV]T PΣ0 20 40 60 80 100 120 140 160 180
Eve
nts
-210
-110
1
10
210
310SM
SM Pair Prod.
)-1H1+ZEUS (0.56 fbp+e
Multi-Leptons at HERA
[GeV]XTP
0 10 20 30 40 50 60 70 80 90 100
Eve
nts
-110
1
10
210
[GeV]XTP
0 10 20 30 40 50 60 70 80 90 100
Eve
nts
-110
1
10
210SMSM Signal
)-1H1+ZEUS (0.59 fb
p+e
[GeV]XTP
0 10 20 30 40 50 60 70 80 90 100
Eve
nts
-110
1
10
210
e+p
H1+ZEUS,0.59 fb−1
2.6σ
1.9σ
Largest observed deviationsfrom the SM at HERA
JHEP 0910:013 (2009)JHEP 1003:035 (2010)
• Identify isolated objects:e, µ, γ, j, ν
• Select events, having at least twoobjects with high PT>20GeV
• Classify into exclusive channelscontaining from 2 to 5 objects
• Compare with SM predictions⇒ good overall agreement
• Find interesting regionswith greatest deviations from SMin kin. distributions (Mall, ΣPT )
⇒ Combine H1 and ZEUS data
HERA at Energy Frontier:
Standard Model is still in excellent shape!
HERA as Super−microscope
11 DIS: Cross sections and Structure Functions
NC
CC
Dominant contribution
Only sensitive at high Q2 ∼ M2Z
Only sensitive at high y
(similarly for pure weak CC analogues: W±2 , xW3 and W±
L )
12 Structure of the proton
F2
dotted lines show the spread in predictionsprior to HERA startup (1992)
12 Structure of the proton
F2
dotted lines show the spread in predictionsprior to HERA startup (1992)
H1 and ZEUS
HE
RA
Incl
usiv
e W
orki
ng G
roup
Aug
ust 2
010
x = 0.00005, i=21x = 0.00008, i=20
x = 0.00013, i=19x = 0.00020, i=18
x = 0.00032, i=17x = 0.0005, i=16
x = 0.0008, i=15x = 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
σ r,N
C(x
,Q2 )
x 2i
+
HERA I+II NC e +p (prel.)Fixed TargetHERAPDF1.5
10-3
10-2
10-1
1
10
10 2
10 3
10 4
10 5
10 6
10 7
1 10 102
103
104
105
Combined HERA e+p data(L = 2 × 250 pb−1)
Bjorken scaling regime at x > 0.05
Large scaling violation at x < 0.01
12 Structure of the proton
F2H1 and ZEUS
HE
RA
Incl
usiv
e W
orki
ng G
roup
Aug
ust 2
010
x = 0.00005, i=21x = 0.00008, i=20
x = 0.00013, i=19x = 0.00020, i=18
x = 0.00032, i=17x = 0.0005, i=16
x = 0.0008, i=15x = 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
σ r,N
C(x
,Q2 )
x 2i
+
HERA I+II NC e +p (prel.)Fixed TargetHERAPDF1.5
10-3
10-2
10-1
1
10
10 2
10 3
10 4
10 5
10 6
10 7
1 10 102
103
104
105
0.2
0.4
0.6
0.8
1
-410 -310 -210 -110 1
0.2
0.4
0.6
0.8
1
HERAPDF1.5 (prel.)
exp. uncert.
model uncert.
parametrization uncert.
x
xf 2 = 10 GeV2Q
vxu
vxd
0.05)×xS (
0.05)×xg (
HE
RA
Str
uctu
re F
unct
ions
Wor
king
Gro
upJu
ly 2
010
H1 and ZEUS HERA I+II Combined PDF Fit
0.2
0.4
0.6
0.8
1
• Precision of (1 − 2)% in the bulk region
• Perfect desciption of the data by NLO QCDover many orders in x and Q2
• using QCD factorisation: σDIS ∼∑
aCa ⊗ fa/puniversal PDFs, fa/p, determined with error bands
Any substructures at 10−18m ?
12 Structure of the proton
F2H1 and ZEUS
HE
RA
Incl
usiv
e W
orki
ng G
roup
Aug
ust 2
010
x = 0.00005, i=21x = 0.00008, i=20
x = 0.00013, i=19x = 0.00020, i=18
x = 0.00032, i=17x = 0.0005, i=16
x = 0.0008, i=15x = 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
σ r,N
C(x
,Q2 )
x 2i
+
HERA I+II NC e +p (prel.)Fixed TargetHERAPDF1.5
10-3
10-2
10-1
1
10
10 2
10 3
10 4
10 5
10 6
10 7
1 10 102
103
104
105
0.2
0.4
0.6
0.8
1
-410 -310 -210 -110 1
0.2
0.4
0.6
0.8
1
HERAPDF1.5 (prel.)
exp. uncert.
model uncert.
parametrization uncert.
x
xf 2 = 10 GeV2Q
vxu
vxd
0.05)×xS (
0.05)×xg (
HE
RA
Str
uctu
re F
unct
ions
Wor
king
Gro
upJu
ly 2
010
H1 and ZEUS HERA I+II Combined PDF Fit
0.2
0.4
0.6
0.8
1
• Precision of (1 − 2)% in the bulk region
• Perfect desciption of the data by NLO QCDover many orders in x and Q2
• using QCD factorisation: σDIS ∼∑
aCa ⊗ fa/puniversal PDFs, fa/p, determined with error bands
Any substructures at 10−18m ?
No. Quarks are still pointlike
]2 [GeV2Q310 410
2/d
QS
Mσ
/ d
2/d
Qσd
0.6
0.8
1
1.2
1.4
1.6
1.8
2
1−p NC 0.16 fb−H1 e
m18−
10⋅ = 0.65 qR
1−p NC 0.28 fb+H1 e
m18−
10⋅ = 0.65 qR
H1
Quark Radius
Upper limit: Rq < 0.65 · 10−3 fm
13 HERAPDF for LHC
W+ cross-section
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HERA
LHC
Tevatron Jet Cross Sections
1.6 < |yjet| < 2.1 (x 10-6)
1.1 < |yjet| < 1.6 (x 10-3)
0.7 < |yjet| < 1.1
0.1 < |yjet| < 0.7 (x 103)
|yjet| < 0.1 (x 106)
KT D=0.7 - fastNLO
HERAPDF1.0(corrected to hadron level)
CDF Data (RunII)(Stat. unc. only)
PT jet [Gev/c]
d2 σ/dy
jet dp
T je
t [nb/
(Gev
/c)]
10-13
10-10
10-7
10-4
10-1
10 2
10 5
10 8
0 100 200 300 400 500 600 700
CDF Data
(Run II)
2011
LHC Data
HERA as a Super-microscope:
• best ever measurement of the proton structure down to 0.001 fm (F2, FL, xF3)
• lots of glue at low x ⇒ in high enery limit QCD processes are gluon-driven
HERA as QCD factory
14 HERA as QCD factory
leadLx
0.1 0.3 0.5 0.7
lead
L/d
xσ
dD
ISσ
1/
-310
-210
-110
H1 DataSIBYLL 2.1EPOS 1.99QGSJET II-03QGSJET 01
H1Forward Photons
*| (
pb
)η∆
/d|
σd
10
210
H1 FPS Data (Prel.)RapGap / 1.23NLO DPDF Fit B / 1.23
H1 Preliminary
1 central jet + 1 forward jet
*|η∆|0 1 2 3
R
0
1
2
*|η∆|0 1 2 3
R
0
1
2
10-1
1
10
10 2
10 3
10 4
ZEUS 82 pb-1
NLO hadr Z0⊗ ⊗
Q2 > 125 GeV2
-2 < ηB jet < 1.5
|cos γh| < 0.65
jet energy scale uncertainty
kT (x 100)
anti-kT(x 10)
SIScone
dσ/
dEje
tT
,B (
pb/G
eV)
0.8
0.9
1
1.1
5 10 15 20 25 30 35 40 45 50 55
kT (+0.05)
anti-kT
SIScone
hadronisation uncertainty
EjetT,B (GeV)
hadr
onis
atio
n co
rrec
tion
(x) 10
log-4 -3.5 -3
(x)
(pb)
10/d
log
σd
0
20
40
60
(x) 10
log-4 -3.5 -3
(x)
(pb)
10/d
log
σd
0
20
40
60
H1 Data (Prel.)
NLO DPDF Jets 2007 (x 0.83)
VFPS DIS Dijets
H1 Preliminary
ZEUS
xL
(1/σ
ep →
eX)d
σ ep →
eX
n/d
xL
ZEUS 40 pb -1 pT2 < 0.476 xL
2 GeV2
ep → ejjXnQ2 < 1 GeV2
ZEUS 40 pb -1
ep → eXnQ2 > 2 GeV2
ZEUS 6 pb -1
ep → eXnQ2 < 0.02 GeV2
0
0.05
0.1
0.15
0.2
0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
H1 and ZEUS
0
0.2
F2 cc_
Q2= 2 GeV2 Q2= 4 GeV2
Oct
ober
200
9
Q2= 6.5GeV2
0
0.5 Q2= 12GeV2 Q2= 20GeV2
HE
RA
Hea
vy F
lavo
ur W
orki
ng G
roup
Q2= 35GeV2
0
0.5 Q2= 60GeV2 Q2=120GeV2
10-4
10-3
10-2
x
Q2=200GeV2
0
0.5
10-4
10-3
10-2
Q2=400GeV2
10-4
10-3
10-2
x
Q2=1000GeV2
HERA (prel.)
MSTW08 NNLOMSTW08 NLOCTEQ 6.6ABKM BMSN
H1 data
data correlated uncertainty
)hadrδ (1+×NLO H1 2006 Fit B
Rapgap
H1 data
data correlated uncertainty
)hadrδ (1+×NLO H1 2006 Fit B
Rapgap
H1 data
data correlated uncertainty
)hadrδ (1+×NLO H1 2006 Fit B
Rapgap
H1 data
data correlated uncertainty
)hadrδ (1+×NLO H1 2006 Fit B
Rapgap
H1 data
data correlated uncertainty
)hadrδ (1+×NLO H1 2006 Fit B
Rapgap
H1 data
data correlated uncertainty
)hadrδ (1+×NLO H1 2006 Fit B
Rapgap
H1 data
data correlated uncertainty
)hadrδ (1+×NLO H1 2006 Fit B
Rapgap
H1 data
data correlated uncertainty
)hadrδ (1+×NLO H1 2006 Fit B
Rapgap
H1 data
data correlated uncertainty
)hadrδ (1+×NLO H1 2006 Fit B
Rapgap
γjetsx
0.2 0.4 0.6 0.8 1
data
/ th
eory
0.5
1
γjetsx
0.2 0.4 0.6 0.8 1
data
/ th
eory
0.5
1
γjetsx
0.2 0.4 0.6 0.8 1
data
/ th
eory
0.5
1(a)H1
[GeV]jet1TE
6 8 10 12 14
data
/ th
eory
0.5
1
[GeV]jet1TE
6 8 10 12 14
data
/ th
eory
0.5
1
[GeV]jet1TE
6 8 10 12 14
data
/ th
eory
0.5
1(b)
IPjetsz
0.2 0.4 0.6 0.8
data
/ th
eory
0.5
1
IPjetsz
0.2 0.4 0.6 0.8
data
/ th
eory
0.5
1
IPjetsz
0.2 0.4 0.6 0.8
data
/ th
eory
0.5
1(c)
H1 data / theory
)hadrδ (1+×NLO H1 2006 Fit B
data correlated uncertainty
)hadrδ (1+×NLO H1 2007 Fit Jets
)hadrδ (1+× 1.23 ×NLO ZEUS SJ
H1 data / theory
)hadrδ (1+×NLO H1 2006 Fit B
data correlated uncertainty
)hadrδ (1+×NLO H1 2007 Fit Jets
)hadrδ (1+× 1.23 ×NLO ZEUS SJ
H1 data / theory
)hadrδ (1+×NLO H1 2006 Fit B
data correlated uncertainty
)hadrδ (1+×NLO H1 2007 Fit Jets
)hadrδ (1+× 1.23 ×NLO ZEUS SJ
H1 data / theory
)hadrδ (1+×NLO H1 2006 Fit B
data correlated uncertainty
)hadrδ (1+×NLO H1 2007 Fit Jets
)hadrδ (1+× 1.23 ×NLO ZEUS SJ
H1 data / theory
)hadrδ (1+×NLO H1 2006 Fit B
data correlated uncertainty
)hadrδ (1+×NLO H1 2007 Fit Jets
)hadrδ (1+× 1.23 ×NLO ZEUS SJ
H1 data / theory
)hadrδ (1+×NLO H1 2006 Fit B
data correlated uncertainty
)hadrδ (1+×NLO H1 2007 Fit Jets
)hadrδ (1+× 1.23 ×NLO ZEUS SJ
H1 data / theory
)hadrδ (1+×NLO H1 2006 Fit B
data correlated uncertainty
)hadrδ (1+×NLO H1 2007 Fit Jets
)hadrδ (1+× 1.23 ×NLO ZEUS SJ
H1 data / theory
)hadrδ (1+×NLO H1 2006 Fit B
data correlated uncertainty
)hadrδ (1+×NLO H1 2007 Fit Jets
)hadrδ (1+× 1.23 ×NLO ZEUS SJ
H1 data / theory
)hadrδ (1+×NLO H1 2006 Fit B
data correlated uncertainty
)hadrδ (1+×NLO H1 2007 Fit Jets
)hadrδ (1+× 1.23 ×NLO ZEUS SJ
ZEUS
0
5
10
15
20
-0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1
(a)γprompt + jet7 < ET γ < 16 GeV
6 < ET jet < 17 GeV
ηγ
dσ/d
ηγ (pb
)
10-1
1
6 8 10 12 14 16
ZEUS (77 pb-1)NLO+had. (KZ) 0.5< µR< 2
NLO+had. (FGH) µR=1kT -fact.+had. (LZ) 0.5< µR < 2
PYTHIA 6.3
HERWIG 6.5
(b)
ET jet (GeV)
dσ/E
T jet (
pb /
GeV
)
0
2
4
6
8
10
-1.5 -1 -0.5 0 0.5 1 1.5 2
(c)
η jet
dσ/d
ηjet (
pb)
0
2
4
6
8
10
0 5 10 15 20 25 30Q2 [GeV2]
b [
GeV
-2]
H1 HERA IH1 HERA II
ZEUS HERA I
Dipole modelGPD model
W = 82 GeV
H1
| [degrees]φ|0 20 40 60 80 100 120 140 160 180
)φ(C
A
-0.6
-0.4
-0.2
0
0.2
0.4
0.6H1 H1 HERA II
φ0.16 cos GPD model
*η0 1 2 3 4 5 6
*ηd dn
N1
0
0.1
0.2
0.3
0.4 H1 Preliminary
* > 1 GeV T
p
° < 155θ < ° 10 lab
H1 data (prelim.)DJANGOHRAPGAP (ALEPH tuning)RAPGAP (default PYTHIA hadronisation)CASCADE
15 Jets at HERA
Precision QCD
αs
from Jet Cross Sections in DISsα
/ GeV r
µ10 210
0.10
0.15
0.20
0.25
/ GeV r
µ10 210
αs
0.10
0.15
0.20
0.25
2 < 100 GeV2H1 data for 5 < Q2 > 150 GeV2H1 data for Q
Central value and exp. unc.
PDF unc.⊕Theory
(th.) ± 0.0016 (PDF)−0.0030+0.0046± 0.0007 (exp.) = 0.1168 sα
[arXiv:0904.3870]2 > 150 GeV2Fit from Q
Running αs in a single experiment!
15 Jets at HERA
Precision QCD
αs
from Jet Cross Sections in DISsα
/ GeV r
µ10 210
0.10
0.15
0.20
0.25
/ GeV r
µ10 210
αs
0.10
0.15
0.20
0.25
2 < 100 GeV2H1 data for 5 < Q2 > 150 GeV2H1 data for Q
Central value and exp. unc.
PDF unc.⊕Theory
(th.) ± 0.0016 (PDF)−0.0030+0.0046± 0.0007 (exp.) = 0.1168 sα
[arXiv:0904.3870]2 > 150 GeV2Fit from Q
)Z
(Msα0.11 0.12 0.13
)Z
(Msα0.11 0.12 0.13
uncertainty
exp.
th.
World averageS. Bethke, Eur. Phys. J. C64, 689 (2009)
D0 incl. midpoint cone jetsPhys. Rev. D80, 111107 (2009)
Aleph Event Shapes, NNLO+NLLAJHEP 08, 036 (2009)
Aleph 3−jet rate, NNLOPhys. Rev. Lett. 104, 072002 (2010)
jets, NLOTZEUS incl. anti−kPhys. Lett. B691, 127 (2010)
jets, NLOTZEUS incl. kPhys. Lett. B 649, 12 (2007)
multijets, NLOT k2H1 low QEur. Phys. J. C67, 1 (2010)
multijets, NLOT norm. k2H1 high QEur. Phys. J. C65, 363 (2010)
H1+ZEUS NC, CC and jet QCD fits, NLOH1−prelim−11−034
trijet, NLO2H1 high QH1−prelim−11−032
dijet, NLO2H1 high QH1−prelim−11−032
inclusive jet, NLO2H1 high QH1−prelim−11−032 Running αs in a single experiment!
HERA results are comparable (and competetive)with the world average
Errors are dominated by theoretical uncertainties(calculations are lacking HO (NNLO) terms)
15 Jets at HERA
Precision QCD
αs
from Jet Cross Sections in DISsα
/ GeV r
µ10 210
0.10
0.15
0.20
0.25
/ GeV r
µ10 210
αs
0.10
0.15
0.20
0.25
2 < 100 GeV2H1 data for 5 < Q2 > 150 GeV2H1 data for Q
Central value and exp. unc.
PDF unc.⊕Theory
(th.) ± 0.0016 (PDF)−0.0030+0.0046± 0.0007 (exp.) = 0.1168 sα
[arXiv:0904.3870]2 > 150 GeV2Fit from Q
)Z
(Msα0.11 0.12 0.13
)Z
(Msα0.11 0.12 0.13
uncertainty
exp.
th.
World averageS. Bethke, Eur. Phys. J. C64, 689 (2009)
D0 incl. midpoint cone jetsPhys. Rev. D80, 111107 (2009)
Aleph Event Shapes, NNLO+NLLAJHEP 08, 036 (2009)
Aleph 3−jet rate, NNLOPhys. Rev. Lett. 104, 072002 (2010)
jets, NLOTZEUS incl. anti−kPhys. Lett. B691, 127 (2010)
jets, NLOTZEUS incl. kPhys. Lett. B 649, 12 (2007)
multijets, NLOT k2H1 low QEur. Phys. J. C67, 1 (2010)
multijets, NLOT norm. k2H1 high QEur. Phys. J. C65, 363 (2010)
H1+ZEUS NC, CC and jet QCD fits, NLOH1−prelim−11−034
trijet, NLO2H1 high QH1−prelim−11−032
dijet, NLO2H1 high QH1−prelim−11−032
inclusive jet, NLO2H1 high QH1−prelim−11−032
?
Grand Unification?
Precision does matter!
16 QCD at low x
e+
p
e+
γ*
q
q
Q2
x
x0, k ⊥ 0
x i, k ⊥ i
x i+1 , k ⊥ i+1
Lots of glue in the proton ⇒ long gluon cascade at low x. Perturbative expansion
of evolution equations ∼ ∑mnAmn ln(Q2)m ln(1/x)n hard to calculate explicitely
⇒ approximations needed
DGLAP: resums ln(Q2)n terms, neglecting ln(1/x)n terms
strong kT ordering in partonic cascade
BFKL: resums ln(1/x)n terms
no kT ordering in partonic cascade ⇒ more hard gluons
are radiated far from the hard interaction vertex
CCFM: angular ordered parton emission ⇒reproduces DGLAP at large x and BFKL at x → 0
• How long is partonic cascade at HERA, at small x?
• Do the ln(1/x)n terms play a major role in parton dynamics as suggested by BFKL?
⇒ Look at (multi)jet final states at low x in different configurations
17 Jets at HERA: New dynamics?
e+
p
e+
γ*
q
q
Q2
x
x0, k ⊥ 0
x i, k ⊥ i
x i+1 , k ⊥ i+1
look at different topologies
especially with forward jets
jet, Et>4 GeV
17 Jets at HERA: New dynamics?
e+
p
e+
γ*
q
q
Q2
x
x0, k ⊥ 0
x i, k ⊥ i
x i+1 , k ⊥ i+1
look at different topologies
especially with forward jets
jet, Et>4 GeV
1 forward jet + 2 central jets
10 3
10 4
10 5
10−4
10−3
Datacorr. errorO(αs
3)O(αs
2)
x
dσ/d
x [p
b] H1
NLO DGLAP is OK
17 Jets at HERA: New dynamics?
e+
p
e+
γ*
q
q
Q2
x
x0, k ⊥ 0
x i, k ⊥ i
x i+1 , k ⊥ i+1
look at different topologies
especially with forward jets
jet, Et>4 GeV
1 forward jet + 2 central jets
10 3
10 4
10 5
10−4
10−3
Datacorr. errorO(αs
3)O(αs
2)
x
dσ/d
x [p
b] H1
NLO DGLAP is OK
2 forward jets + 1 central jet
10 3
10 4
10 5
10−4
10−3
Datacorr. errorO(αs
3)O(αs
2)
xdσ
/dx
[pb] H1
NLO DGLAP fails at low x
NLO DGLAP insufficientat low x ⇒ Room fornon-DGLAP dynamics!
Diffraction
e
p
P
M
e
p
O
p
e
M
n
π,η,...
π
o
LRG
Diffraction
e
p
P
M
e
p
O
p
e
M
n
π,η,...
π
o
D i f f r a c t i o n
LRG
Diffraction in HEP =
Colorless exchange carrying vacuum quantum numbers
18 Two approaches to Strong Interactions
1. Regge Pole Model ⇒ RFT 2. Quark-Parton Model ⇒ QCD
t
s
m1
m2
M1
M2
g1
g2
α(t)
A(s, t) =
g1(m1,M1, t)g2(m2,M2, t)sα(t)±(−s)α(t)
sin(πα(t))
σab =∫fi/a(xi, µ
2) · fj/b(xj, µ2) · σ̂ij(xi, xj, µ2)
hadronic language sub-hadronic language
Ultimate goal: derive (1) from (2)
19 RFT: soft hh scattering vs QCD: deep inelastic ep scattering
• Hadronic degrees of freedom • Partonic degrees of freedom
• Validity: large s ≫ t • Low x: W 2 ≫ Q2, t (Q2/W 2 ≃ x ≪ 1)
• IP dominates: αIP (0) > αIR(0) • gluons dominate: xg(x) ≫ xqval(x)
→ σtot ∝ sαIP (0)−1 F2(x, Q2) ∝ xg(x) ∼ x−λ
• Unitarity corrections unavoidable • Saturation of the xg(x)
(σtot ≤ ln2(s/s0) at s → ∞) (non-linear effects, shadowing, ...)
• When? ssat =? • xsat(Qsat) =?
• First to be seen in diffraction: σD ∝ s2(α−1) • First to be seen in diffraction: σD ∝ |xg(x)|2
⇒ Diffraction ≡ Physics of the Pomeron, ⇒ Diffraction ≡ Gluodynamics,the essence of strong interactions the essence of QCD
(in high energy limit) .
20 Diffraction at HERA
� Fundamental aim: understand high energy limit of QCD (gluodynamics; CGC ?)
� Novelty: for the first time probe partonic structure of diffractive exchange
� Practical motivations: study factorisation properties of diffraction; try to transport tohh scattering (e.g. predict diffractive Higgs production at LHC)
2
β
′(MY )
xIP = ξ =Q2+M2
XQ2+W 2
(momentum fraction of colour singlet exchange)
β = Q2
Q2+M2X
= xq/IP = xxIP
(fraction of exchange momentum, coupling to γ∗)
t = (p− p′)2
(4-momentum transfer squared)
Experimental methods:
1) selecting LRG events
2) detecting p in Roman Pots(60 − 220 m from IP) FPS, VFPS
21 Inclusive Diffraction in DIS
ZEUS-1993
First observation
of diffraction in DIS
1992 data, 24.7 nb−1
21 Inclusive Diffraction in DIS
ZEUS-1993
First observation
of diffraction in DIS
1992 data, 24.7 nb−1
Current H1 status H1 VFPS PreliminaryH1 FPS PreliminaryH1 LRG Preliminary x 0.81
H1 LRG Published x 0.81H1 2006 DPDF Fit B x 0.81H1 2006 DPDF Fit B x 0.81 (extrapol.)
D(3
)r
σIP
x
210 10 210 10 210 10 210 10 210 10 210 10]2 [GeV2Q
0.020.040.06 =0.017β
=0.0003IPx
0.020.040.06 =0.027β
0.020.040.06 =0.043β
0.020.040.06 =0.067β
0.020.040.06 =0.110β
0.020.040.06 =0.170β
0.020.040.06 =0.270β
0.020.040.06 =0.430β
0.020.040.06 =0.670β
2
0.020.040.06 =0.0010IPx
2
0.020.040.06
2
0.020.040.06
2
0.020.040.06
2
0.020.040.06
2
0.020.040.06
2
0.020.040.06
2
0.020.040.06
2
0.020.040.06
2
0.020.040.06 =0.0030IPx
2
0.020.040.06
2
0.020.040.06
2
0.020.040.06
2
0.020.040.06
2
0.020.040.06
2
0.020.040.06
2
0.020.040.06
2
0.020.040.06
10 210
0.02
0.04
0.06 =0.011β
10 210
0.02
0.04
0.06 =0.022β
10 210
0.02
0.04
0.06 =0.045β
10 210
0.02
0.04
0.06 =0.089β
10 210
0.02
0.04
0.06 =0.178β
10 210
0.02
0.04
0.06 =0.355β
10 210
0.02
0.04
0.06 =0.708β
210
0.02
0.04
0.06
210
0.02
0.04
0.06
210
0.02
0.04
0.06
210
0.02
0.04
0.06
210
0.02
0.04
0.06
210
0.02
0.04
0.06
210
0.02
0.04
0.06
2
0.02
0.04
0.06
2
0.02
0.04
0.06
2
0.02
0.04
0.06
2
0.02
0.04
0.06
2
0.02
0.04
0.06
2
0.02
0.04
0.06
2
0.02
0.04
0.06
2
0.02
0.04
0.06
2
0.02
0.04
0.06
2
0.02
0.04
0.06
2
0.02
0.04
0.06
2
0.02
0.04
0.06
2
0.02
0.04
0.06
2
0.02
0.04
0.06
2
0.020.040.06 =0.002β
=0.035IPx
2
0.020.040.06 =0.006β
2
0.020.040.06 =0.018β
2
0.020.040.06 =0.056β
2
0.020.040.06 =0.178β
2
0.020.040.06 =0.562β
0.020.040.06 =0.050IPx
0.020.040.06
0.020.040.06
0.020.040.06
0.020.040.06
0.020.040.06
2
0.020.040.06 =0.075IPx
2
0.020.040.06
2
0.020.040.06
2
0.020.040.06
2
0.020.040.06
2
0.020.040.06
10 210
0.020.040.06 =0.002β
=0.010IPx
10 210
0.020.040.06 =0.004β
10 210
0.020.040.06 =0.007β
210
0.020.040.06 =0.013IPx
210
0.020.040.06
210
0.020.040.06
2
0.020.040.06 =0.017IPx
2
0.020.040.06
2
0.020.040.06
2
0.020.040.06 =0.022IPx
2
0.020.040.06
2
0.020.040.06
LRG
VFPS
FPS
scaling violation up to
very large β (= x of IP )
• Compelling confirmation of the NLO QCD picture of diffractionover a wide kinematic range. Clear candidate for the textbook!
• Diffractive PDFs are determined from these data. Are they universal?
22 Factorisation properties in diffraction
pp
X (M )X
e
QCD collinearfactorisation at
fixed x , t
(b)
(x )IP
(t)
e
(Q )2g*
}
}
IP
γ
ppIP
IPq
qγ
ppIP= x
QCD versus Regge factorisation
QCD factorisation(rigorously proven for
DDIS by Collins et al.):
Regge factorisation(conjecture, e.g. RPM
by Ingelman,Schlein):
σD(4)r ∝ ∑
i σ̂γ∗i(x,Q2) ⊗ fDi (x,Q2;xIP , t)
• σ̂γ∗i – hard scattering part, same as in inclusive DIS
• fDi
– diffractive PDF’s, valid at fixed xIP , t which obey (NLO) DGLAP
FD(4)2 (xIP , t, β,Q
2) = Φ(xIP , t) · F IP2 (β,Q2)
• In this case shape of diffractive PDF’s is independent of xIP , t
while normalization is controlled by Regge flux Φ(xIP , t)
23 QCD Factorisation Tests in Diffraction at HERA
QCD Factorisation holds in DIS regime, e.g.:
(x) 10
log-4 -3.5 -3
(x)
(pb
)1
0/d
log
σd
0
20
40
60
(x) 10
log-4 -3.5 -3
(x)
(pb
)1
0/d
log
σd
0
20
40
60
H1 Data (Prel.)
NLO DPDF Jets 2007 (x 0.83)
VFPS DIS Dijets
H1 Preliminary
( p
b )
IP/d
zσd
200
400
600
800H1 FPS Data (Prel.)RapGap / 1.23NLO DPDF Fit B / 1.23
H1 Preliminary
2 central jets
IPz0 0.5 1
0.51
1.52
R
IPz0 0.5 1
0.51
1.52
23 QCD Factorisation Tests in Diffraction at HERA
QCD Factorisation holds in DIS regime, e.g.:
(x) 10
log-4 -3.5 -3
(x)
(pb
)1
0/d
log
σd
0
20
40
60
(x) 10
log-4 -3.5 -3
(x)
(pb
)1
0/d
log
σd
0
20
40
60
H1 Data (Prel.)
NLO DPDF Jets 2007 (x 0.83)
VFPS DIS Dijets
H1 Preliminary
( p
b )
IP/d
zσd
200
400
600
800H1 FPS Data (Prel.)RapGap / 1.23NLO DPDF Fit B / 1.23
H1 Preliminary
2 central jets
IPz0 0.5 1
0.51
1.52
R
IPz0 0.5 1
0.51
1.52
However, it breaks down at Tevatron ...
H1 2002 σrD QCD Fit (prel.)
QCD fit to ZEUS 97 data
CDF IP+RR
β
FJJD (
β)
10-1
1
10
10 2
10-1
Tevatron vs HERA
23 QCD Factorisation Tests in Diffraction at HERA
QCD Factorisation holds in DIS regime, e.g.:
(x) 10
log-4 -3.5 -3
(x)
(pb
)1
0/d
log
σd
0
20
40
60
(x) 10
log-4 -3.5 -3
(x)
(pb
)1
0/d
log
σd
0
20
40
60
H1 Data (Prel.)
NLO DPDF Jets 2007 (x 0.83)
VFPS DIS Dijets
H1 Preliminary
( p
b )
IP/d
zσd
200
400
600
800H1 FPS Data (Prel.)RapGap / 1.23NLO DPDF Fit B / 1.23
H1 Preliminary
2 central jets
IPz0 0.5 1
0.51
1.52
R
IPz0 0.5 1
0.51
1.52
However, it breaks down at Tevatron ......due to soft remnant rescattering (S ∼ 0.15)
H1 2002 σrD QCD Fit (prel.)
QCD fit to ZEUS 97 data
CDF IP+RR
β
FJJD (
β)
10-1
1
10
10 2
10-1
Tevatron vs HERA
23 QCD Factorisation Tests in Diffraction at HERA
QCD Factorisation holds in DIS regime, e.g.:
(x) 10
log-4 -3.5 -3
(x)
(pb
)1
0/d
log
σd
0
20
40
60
(x) 10
log-4 -3.5 -3
(x)
(pb
)1
0/d
log
σd
0
20
40
60
H1 Data (Prel.)
NLO DPDF Jets 2007 (x 0.83)
VFPS DIS Dijets
H1 Preliminary
( p
b )
IP/d
zσd
200
400
600
800H1 FPS Data (Prel.)RapGap / 1.23NLO DPDF Fit B / 1.23
H1 Preliminary
2 central jets
IPz0 0.5 1
0.51
1.52
R
IPz0 0.5 1
0.51
1.52
However, it breaks down at Tevatron ......due to soft remnant rescattering (S ∼ 0.15)
H1 2002 σrD QCD Fit (prel.)
QCD fit to ZEUS 97 data
CDF IP+RR
β
FJJD (
β)
10-1
1
10
10 2
10-1
Tevatron vs HERA
⇒ Test it in photoproduction:
p(P) )Y
Y (P
IPx
IPz (v)
* (q)γ (u)
e(k) e(k’)
jet
jet)
XX(P
GAP
remnant
e(k) e(k’)
* (q)γ
(u)
jet 12M )X
X(P
(v)IPz
remnant
GAP
p(P) )Y
Y (P
jet
remnant
(a) (b)
12M
IPx
xγ
xγ
direct, xγ=1 (DIS-like) resolved, xγ<1 (hadron-like)
23 QCD Factorisation Tests in Diffraction at HERA
QCD Factorisation holds in DIS regime, e.g.:
(x) 10
log-4 -3.5 -3
(x)
(pb
)1
0/d
log
σd
0
20
40
60
(x) 10
log-4 -3.5 -3
(x)
(pb
)1
0/d
log
σd
0
20
40
60
H1 Data (Prel.)
NLO DPDF Jets 2007 (x 0.83)
VFPS DIS Dijets
H1 Preliminary
( p
b )
IP/d
zσd
200
400
600
800H1 FPS Data (Prel.)RapGap / 1.23NLO DPDF Fit B / 1.23
H1 Preliminary
2 central jets
IPz0 0.5 1
0.51
1.52
R
IPz0 0.5 1
0.51
1.52
However, it breaks down at Tevatron ......due to soft remnant rescattering (S ∼ 0.15)
H1 2002 σrD QCD Fit (prel.)
QCD fit to ZEUS 97 data
CDF IP+RR
β
FJJD (
β)
10-1
1
10
10 2
10-1
Tevatron vs HERA
⇒ Test it in photoproduction:
p(P) )Y
Y (P
IPx
IPz (v)
* (q)γ (u)
e(k) e(k’)
jet
jet)
XX(P
GAP
remnant
e(k) e(k’)
* (q)γ
(u)
jet 12M )X
X(P
(v)IPz
remnant
GAP
p(P) )Y
Y (P
jet
remnant
(a) (b)
12M
IPx
xγ
xγ
direct, xγ=1 (DIS-like) resolved, xγ<1 (hadron-like)
S = 0.58 ± 0.21
• Global, xγ-independent suppresion factor is observed – somewhat unexpected
⇒ Details of factorisation breaking mechanism in γp at HERA are not fully understood yet
24 Vector Mesons at HERA
αIP(t)=α(0)+α′t
soft IPomeron exchange hard IPomeron diagrams
24 Vector Mesons at HERA
Exclusive VM production at HERA – a nice tool to study ‘soft’ vs ‘hard’ Pomeron regimes
αIP(t)=α(0)+α′t
soft IPomeron exchange hard IPomeron diagramsHard scales: Q2,MV , t
Predictions
αIP (0) ≃ 1.08 / 1.20
α′IP ≃ 0.25 / 0.0
Universal scale µ2 = (Q2+M2V )/4
24 Vector Mesons at HERA
Exclusive VM production at HERA – a nice tool to study ‘soft’ vs ‘hard’ Pomeron regimes
αIP(t)=α(0)+α′t
soft IPomeron exchange hard IPomeron diagramsHard scales: Q2,MV , t
Predictions
αIP (0) ≃ 1.08 / 1.20
α′IP ≃ 0.25 / 0.0
Universal scale µ2 = (Q2+M2V )/4
transition from soft to hard regime at µ2 ≃ 4÷5 GeV2
25 Vector Mesons at HERA:t−dependence
dσ/dt ∼ e−b|t| → diffractive peak (approximated from Bessel function)
b = (R/2)2 → transverse size of the target (geometric picture)
25 Vector Mesons at HERA:t−dependence
dσ/dt ∼ e−b|t| → diffractive peak (approximated from Bessel function)
b = (R/2)2 → transverse size of the target (geometric picture)
Predictions: b = b0 + 4α′IP ln(W/W0);
soft IP : shrinkage of diffractive peak (α′IP =0.25); large b0 ≈ 10 GeV−2
hard IP : no (or small) shrinkage (α′IP <0.1); small b0 ≈ 5 GeV−2
25 Vector Mesons at HERA:t−dependence
dσ/dt ∼ e−b|t| → diffractive peak (approximated from Bessel function)
b = (R/2)2 → transverse size of the target (geometric picture)
Predictions: b = b0 + 4α′IP ln(W/W0);
soft IP : shrinkage of diffractive peak (α′IP =0.25); large b0 ≈ 10 GeV−2
hard IP : no (or small) shrinkage (α′IP <0.1); small b0 ≈ 5 GeV−2
3
4
5
6
b(W
γp)
[GeV
-2]
⟨Q2⟩ = 0.05 GeV2H1a)
3
4
5
6
Wγp [GeV]
b(W
γp)
[GeV
-2]
50 100 200
H1ZEUS2D-Fit
⟨Q2⟩ = 8.9 GeV2H1b)
Example: shrinkage in γ∗p → J/ψp
Q2 < 1 GeV2:
α′IP = 0.164 ± 0.028 ± 0.030
Q2 = 2 − 80 GeV2:
α′IP = 0.019 ± 0.139 ± 0.076
25 Vector Mesons at HERA:t−dependence
dσ/dt ∼ e−b|t| → diffractive peak (approximated from Bessel function)
b = (R/2)2 → transverse size of the target (geometric picture)
Predictions: b = b0 + 4α′IP ln(W/W0);
soft IP : shrinkage of diffractive peak (α′IP =0.25); large b0 ≈ 10 GeV−2
hard IP : no (or small) shrinkage (α′IP <0.1); small b0 ≈ 5 GeV−2
Dipole picture interpretation:
b = bVM + bp
bVM ∼ 1/(Q2 +M2VM)
bp → size of the gluons area:
〈r2〉 = 2bp·(~c)2 ≃ 0.6 fm
Gluons confinement area (0.6 fm) is smaller than the proton size (0.8 fm)
26 Summary
� Standard Model survived 1 fb−1 of HERA data and is still in a good shape.Next challenge is now coming from the LHC - stay tuned!
� Combining H1 and ZEUS data allowed proton structure to be measuredwith unprecedental precision
� NLO DGLAP is surprisingly successful down to lowQ2 and low x in describ-ing bulk of HERA data. However, some room for parton evolution beyondDGLAP is found at specific phase space corners ⇒ important message forLHC
� Gained new insights into high energy diffraction: Pomeron under the HERAmicroscope shows complicated interplay of soft and hard phenomena.Understanding colour singlet exchange remains a major challenge in QCD
� Is this the end of DIS experiments? Or what’s next at the horizon?
27This is dummy text in order to force correct page orientation (landscape). Attempt to cure autorotation by pdf conversion
e±p(60 − 140)GeV × 7000 GeV
Project under discussion For late LHC period:
∼ 2022−2032
√s ≈ (4 − 6)×HERA L ≈ (50 − 100)×HERA
28 100 years of studying the structure of matter
� Fixed target experiments
⊲ Rutherford – 1911 (7 MeV, αAu)structure of atoms ⇒ planetary model ⇒ quantum mechanics
⊲ Hofstadter – 1953 (400 MeV, eA)structure of the nucleus; determination of the size of A and p
⊲ SLAC – 1968 (20 GeV, ep)structure of the proton ⇒ quarks ⇒ QPM
⊲ SPS@CERN – 1976 (EMC, NA4, etc. studying DIS with µ beam)
� Collider experiments
⊲ HERA – 1992 (27.5 × 920 GeV ep)gluon dominated proton (and Pomeron); low x QCD; EW sector of SM
⊲ LHeC – 2022 (60 × 7000 GeV, ep/eA) – not approved yet
non-linear QCD? Strong parton saturation? BSM phenomena?