Äîêóìåíò âçÿò èç êýøà ïîèñêîâîé ìàøèíû. Àäðåñ îðèãèíàëüíîãî äîêóìåíòà : http://qfthep.sinp.msu.ru/talks2013/buniatyan.qfthep.pdf Äàòà èçìåíåíèÿ: Tue Jun 25 23:01:20 2013 Äàòà èíäåêñèðîâàíèÿ: Thu Feb 27 20:24:15 2014 Êîäèðîâêà: Ïîèñêîâûå ñëîâà: m 35

QFTHEP 2013 The XXI International Workshop High Energy Physics and Quantum Field Theory June 23­30, 2013 Saint Petersburg Area

Recent Results from the H1 Experiment at HERA
Armen Buniatyan
Physikalisches Institut Ruprecht-Karls-UniversitÄt Heidelberg

On behalf of the H1 Collaboration


HERA
The world's only electron/positron-proton collider at DESY, Hamburg Ee = 27.6 GeV Ep = 920 GeV (also 820, 460 and 575 GeV) (total centre-of-mass energy of collision up to s 320 GeV equivalent to 5 · 1013eV photon beam on a stationary proton target)

Two collider experiments: H1 and ZEUS
Armen Buniatyan Results from H1 experiment

total lumi: 0.5 fb-1 per experiment
QFTHEP 2013 2

HERA-1: 1992 ­ 2000 HERA-2: 2003 - 2007


Recent H1 results

Inclusive measurements proton structure, PDF Electroweak effects Hard diffraction Diffractive DIS elastic J/ production diffractive jet production

Hadronic final state Charged particle densities Strangeness, Jet production Target fragmentation

Armen Buniatyan

Results from H1 experiment

QFTHEP 2013

3


Deep Inelastic electron-proton Scattering (DIS) at HERA

DIS ­ a probe of proton structure
*
scattered electron

e

p

proton electron

proton remnant current jet

Armen Buniatyan

Results from H1 experiment

QFTHEP 2013

4


Deep Inelastic electron-proton Scattering (DIS) at HERA
()



Q2=-(k-k')

2

virtuality of exchanged boson: `resolving power' of probe fraction of proton momentum carried by struck quark At HERA x~ 10-6 ­ 1 inelasticity variable: y= Q2/(s·x)

*,Z0 (W±)

x=Q2/2p·q

y=p·q/p·k

At fixed s only two independent kinematic variables, e.g. x and Q
scattered e
Neutral Current (NC)

2



Charged Current (CC)

e

proton

Armen Buniatyan

Results from H1 experiment

QFTHEP 2013

5


DIS at HERA: kinematic coverage HERA: span 5 orders of magnitude in x and Q2 HERA inclusive data are an indispensable input to modern PDF fits Direct overlap with the LHC kinematics: HERA covers x range of the LHC, evolution in Q2 via DGLAP


Armen Buniatyan Results from H1 experiment

HERA= LHC

PDF



ME ME

= PDF



PDF
6

QFTHEP 2013


Inclusive DIS cross sections at high Q2
Final measurement of inclusive NC/CC cross sections at s=319 GeV with H1 detector Data: e-p and e+p polarized e± beams 4 distinct data sets
d /dQ2 [pb/GeV 2]

d/dQ2 cross sections of CC and NC
10
10 0

(all HERA-2 data at Ep=920 GeV)

H1 10 Collaboration
H1 e p NC H1 e+p NC SM e p NC (H1PDF 2012) SM e+p NC (H1PDF 2012)


NC

1 10-1

60< Q < 50.000 GeV , 0.0008 2 2

CC
3 10-3

H1 e p CC



y < 0.9 Pe = 0

10

-7 7

10

3

104

Q2 [GeV2]

JHEP 09 (2012) 061 Armen Buniatyan

Text-book plot illustrating electroweak unification
Results from H1 experiment QFTHEP 2013 7

HERA I + II

Typical precision: NC e+ ~1.5% ; e- ~2.0% CC e± ~4%

H1 e+p CC SM e p CC (H1PDF 2012)


10

-5 5

SM e+p CC (H1PDF 2012)


Inclusive DIS polarised cross sections at high Q2
Polarisation dependence of total CC cross sections SM: ±CC (Pe) = (1±Pe)±CC(0)
[pb]
120

H1 Collaboration
e p X

NC polarisation asymmetry SM: difference in the NC for leptons with different helicity states (due to chiral structure of the neutral EW exchange) Polarisation asymmetry of NC cross section is sensitive to Z interference terms of structure functions


100

tot CC

H1 HERA I H1 HERA II

80

e-

e+p X H1 HERA I H1 HERA II

60 H1PDF 2012 40 Linear Fit

F2 ~ [ (PL)- (PR)]- [ (PL)- (PR)]
Z F2

Z

-

-

+

+

H1 Collaboration
Transformed to Q 2 = 1500 GeV
2

20

HERA I + II

e+
Q2 > 400 GeV y < 0.9 0 -100 -50 0 50
2

1
H1 H1PDF 2012

100

Linear scaling with P

Pe [%]

e

0.5

Extrapolated cross sections 0 - at Pe=+1 for e- at Pe=-1 for e+ Text-book plot demonstrating the absence of right handed weak current
Armen Buniatyan

0

10-1

First measurement of F

2

Z

x

1

structure function
JHEP 09 (2012) 061 QFTHEP 2013 8

Results from H1 experiment

HERA II


Inclusive DIS cross sections
unpolarised NC cross e-p and e+p reduced cross sections
JHEP 09 (2012) 061

2 2 Y± = dx dQ xQ4

d 2

NC e ±p 2

y2 FL , Y± = 1 ± (1 - y) F2 - Y±
NC(x,Q2) â 2i
10
6

2

H1 Collaboration
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

H1 NC e p, P e = 0 H1 NC e+p, P e = 0 H1 Low Q2 Fixed Target H1PDF 2012, e p




reduced cross section r (x, Q 2 )

10 10

5

F2 = x



e [q(x) + q (x)]
2 q

4

H1PDF 2012, e+p

103 102 10

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

dominant contribution to cross section Very high precision Combined H1 data probe the proton over nearly 5 orders of magnitude Scaling violation Text-book measurement !

1 10-1 10-2 10-3 1

x = 0.25, i = 2

x = 0.40, i = 1

x = 0.65, i = 0

10

102

103

104

105

106

Q2 [GeV2]

Armen Buniatyan

Results from H1 experiment

QFTHEP 2013

9

HERA I + II


NLO QCD fit to inclusive DIS cross sections
NLO QCD fit to all published NC and CC H1 data with HERAFitter

xf(x)

0.8

H1 Collaboration
Q2 = 10 GeV
2

0.6
xg(

H1PDF 2012 experimental uncertainty + model uncertainty + parametrisation unc. f s=0.5 fit

xu

v

â 0.05)

0.4
xS(â
0.05)

xd

v

0.2 0 10-4

10-3

10-2

10-1

x

H1PDF 2012 Improvement in precision for all PDFs in the full x range
JHEP 09 (2012) 061 Armen Buniatyan 10 Results from H1 experiment QFTHEP 2013


Recent H1 results

Inclusive measurements proton structure, PDF Electroweak effects Hard diffraction Diffractive DIS elastic J/ production diffractive jet production

Hadronic final state Charged particle densities Strangeness, Jet production Target fragmentation

Armen Buniatyan 11

Results from H1 experiment

QFTHEP 2013


Charged particle densities in DIS
A large amount of the experimental data on charged particle production spectra has been accumulated during last decades. However the underlying dynamics of hadron production in high energy particle interaction is still not fully understood. Several mechanisms contribute to hadron production

PDF



Parton dynamics



Hadronisation

HFS

Different kinematic ranges sensitive to different effects

Low pT region · Hadronisation effects dominate High pT region · Parton dynamics effects dominate
New H1 results on charged particle spectra:
Analyses performed in *p frame (*, pT*)
Armen Buniatyan Results from H1 experiment QFTHEP 2013 12

with proton energy Ep =920 GeV (s = 319 GeV) and proton energy Ep=460 GeV (s = 225 GeV)


Parton evolution models

strong kT ordering k2T0<<...<
DGLAP:

beyond DGLAP:
random walk in kT

CCFM model valid for both: large and small x CASCADE MC

Colour Dipole Model (CDM) BFKL like parton evolution) valid at low x and not large Q DJANGOH MC
2

Hadronisation parameters tuned to e+e- data (ALEPH tune)
Armen Buniatyan Results from H1 experiment QFTHEP 2013 13


Charged particle density: sensitivity to parton cascade models
H1 data DJANGOH RAPGAP CASCADE Herwig++

1 dn N d *

1 dn N d *

3
T

0.4

H1 data DJANGOH RAPGAP

CASCADE Herwig++

p * < 1 GeV

H1

1 < p * < 10 GeV
T

H1

0.3
2

0.2
1

0.1

0 0

1

2

3

4

5

6 *

0 0

1

2

3

4

5

6 *

All models (except CASCADE) describe the data within PDF uncertainties

Strong sensitivity to parton dynamics at large pT DGLAP models (RAPGAP and HERWIG) underestimate the data for *<3

Best description at all pT* by DJANGOH (CDM)
Armen Buniatyan Results from H1 experiment

EPJ C73 (2013) 2406 QFTHEP 2013 14


Charged particle density: sensitivity to hadronisation models
H1 data RAPGAP ALEPH tune Professor tune Default PYTHIA hadronisation
H1 data RAPGAP ALEPH tune Professor tune Default PYTHIA hadronisation

1 dn N d *

p * < 1 GeV
T

H1

1 dn N d *

3

0.4
1 < p * < 10 GeV
T

H1

0.3

2
0.2

1
0.1

0 0

1

2

3

4

5

6 *

0 0

1

2

3

4

5

6 *

· ·

Large sensitivity to the tuning of hadronisation parameters Data are best described by ALEPH tune (e+e-)

· ·

Essentially no sensitivity to hadronisation expected None of the tunes describes the data
EPJ C73 (2013) 2406

Armen Buniatyan

Results from H1 experiment

QFTHEP 2013

15


Charged particle density in DIS at low Ep Use data with reduced proton beam energy Ep = 460 GeV to achieve good acceptance and high resolution in * closer to the central region
Central Central 0*~<0 < * 1.5
p -direction

Current Current 1.5*~ < 5 < * 2

- direction

-low Q²: 5 < Q² < 10 GeV² - high y: 0.35 < y < 0.8
*
Charged particle spectra 2.0 < * < 2.5

p
.

Charged particle spectra 0 < * < 0.5

MC/Data

2 1.8 1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 10
-1

MC/Data

H1 Preliminary

2 1.8 1.6 1.4 1.2 1 0.8

H1 Preliminary

"Central" region

Current (*) region

H1 data Djangoh * 0.61 Rapgap * 0.62

0.6 0.4 0.2 1 10 pT [GeV/c] * 10-1

H1 data Djangoh * 0.61 Rapgap * 0.62

1

10 pT [GeV/c] *

Models don't describe the pT*,* double differential cross sections
Armen Buniatyan Results from H1 experiment QFTHEP 2013 16


Very Forward Neutron and Photon Production in DIS
Measurements of Forward Particles are important for the understanding of proton fragmentation mechanisms, and, in particular, interesting for tuning hadron interaction in Cosmic Ray models.
Very forward, p fragmentation LAB >7.9
0 < *<0 *~ 1.5

Central Central

Current Current 1.5*~*< 5 < 2

p -direction

- direction

ep collisions ­ a clean environment to study
the proton fragmentation

Forward Photons are produced mainly in 0 decay from hadronisation of the proton remnant Forward Neutrons are produced in proton fragmentation and by the -exchange mechanisms, p n++

p
.

*

Forward photons and neutrons ( >7.9) measured in the FNC Calorimeter (106m from IP) Lab

n

QFTHEP 2013 17

Armen Buniatyan

Results from H1 experiment


Monte Carlo Models
MC models: - inclusive DIS: LEPTO - LO matrix elements+leading log parton shower ARIADNE - LO matrix elements+color dipole model (CDM) - Pion exchange model: RAPGAP-



Hadronic interaction Cosmic Rays (CR) models: QGSJET 01, QGSJET II-03: (Kalmykov, Ostapchenko) EPOS 1.9: (Pierog, Werner) SIBYLL 2.1: (Engel, Fletcher, Gaisser, Lipari, Stanev) Differences in modeling - mini-jet production, formation of color strings and fragmentation, treatment of saturation effects, multiparton interaction, treatment of hadron remnants.

study the energy (W) dependence of xF=2p*||/W distributions
Armen Buniatyan Results from H1 experiment QFTHEP 2013 18


Very forward photons and neutrons: 1/

DIS

d/dxF distributions vs W

H1prelim-13-012

70 < W < 130 GeV

130 < W < 190 GeV

190 < W < 250 GeV

- Photon rate in all MC models used is significantly (70%) higher than in the data at all W - CDM predict much harder xF spectra

70 < W < 130 GeV

130 < W< 190 GeV

190 < W < 245 GeV

Neutron rate described by combination of -exchange (RAPGAP) and 'standard' fragmentation models
Armen Buniatyan Results from H1 experiment QFTHEP 2013 19


Very forward photons and neutrons: comparison with the Cosmic Ray hadronic interaction models
Forward Photons

F

1/DIS d/dx

H1 Preliminary

10-1

10-2

70 < W < 130 GeV H1 Data (prel.) SIBYLL 2.1

10-3

EPOS 1.99 QGSJET II-03 QGSJET 01

0.1

0.2

0.3

0.4

0.5

0.6

0.7

x

F

· Large differences between the Cosmic Ray model predictions · None of models describes simultaneously the photon and neutron measurements

H1prelim-13-012 Armen Buniatyan Results from H1 experiment QFTHEP 2013 20


Jet production in DIS
QPM QCD Compton BGF Boson-gluon fusion BGF +



0 S



1 S



1 S



2 S

Measurements of jets provide a powerful ground for precision QCD test Cross section depends on: QCD matrix elements, strong coupling s, PDF of the proton Jets are directly sensitive to s and gluons already in LO: ~s·g(x) extract strong coupling s with high precision combined inclusive DIS and jet analyses help to improve constraining gluon density

Armen Buniatyan

Results from H1 experiment

QFTHEP 2013

21


Normalised Jet Cross Sections in DIS at high Q2
H1prelim-12-031

Inclusive jet, 2-jet, 3-jet production ·photon virtuality 150 < Q2 <15000 GeV
2

longitudinally invariant kT jet algorithm in the Breit frame collinear and infrared safe · high precision- 1% jet energy scale uncertainty · data are well described by NLO calculation

Combined NLO fit to normalised inclusive, dijet and trijet cross sections S(MZ)=0.1163 ± 0.0011 (exp) ± 0.0014 (PDF) ± 0.0008 (had) ± 0.0039 (theory)
Armen Buniatyan Results from H1 experiment QFTHEP 2013 22


Comparison of recent S(MZ) values

HERA jet data among the most precise data for precision test of QCD pQCD calculations in general describe the data extractions of s(Mz) yield values consistent with the world average and having an experimental precision competitive with other extraction methods Theory uncertainty dominate NNLO needed
Armen Buniatyan Results from H1 experiment QFTHEP 2013 23


Recent H1 results

Inclusive measurements proton structure, PDF Electroweak effects Hard diffraction Diffractive DIS elastic J/ production diffractive jet production

Hadronic final state Charged particle densities Strangeness, Jet production Target fragmentation

Armen Buniatyan 24

Results from H1 experiment

QFTHEP 2013


Diffraction in ep collisions
One of first HERA surprises: ~10% of DIS events have no activity in proton direction, i.e. they are from diffractive interactions

2

· t-channel exchange of vacuum quantum numbers
· proton survives the collision intact or dissociates


rapidity gap

X Y

to low mass state, MY ~ large rapidity gap

O(mp

)

t

· small t (four-momentum transfer), small xIP (fraction of proton momentum); MX «W

access to the structure of the colour-singlet exchange description in terms of diffractive parton densities different experimental methods to tag diffraction: - leading proton tagging - large rapidity gap
Armen Buniatyan Results from H1 experiment QFTHEP 2013 25


H1/ZEUS Combined Inclusive Diffractive DIS Cross Sections measured with forward proton spectrometers
EPJ C72 (2012) 2175

Proton Spectrometer data in
H1 and ZEUS
H1 FPS HERA II ZEUS LPS 2
D(3)

H1 FPS HERA I HERA ZEUS LPS 1 0.09<|t|<0.55 GeV2

0.09<|t|<0.55 GeV2

xIP

0.225 0.2 0.175 0.15 0.125 0.1 0.075 0.05 0.025 0

xIP=0.05 =0.018 (x 6)

Consistency between H1 and ZEUS data sets Combination method uses iterative 2 minimization and include full error correlations Profit from different detectors: Two experiments `calibrate' each other resulting in reduction of systematic uncertainties

r

=0.056 (x 3)

=0.18
2

10

Q (GeV )

10 2

2

Combined data have ~25% smaller uncertainties then the most precise data alone

Important input to diffractive PDFs
Armen Buniatyan Results from H1 experiment QFTHEP 2013 26


Diffractive Photoproduction of J/ mesons
EPJ C73 (2013) 2466

J/ e+e-

J/ +-

clean experimental signature
Elastic: ep e+ J/ +p Proton dissociation : ep e+ J/ +Y

Armen Buniatyan

Results from H1 experiment

QFTHEP 2013

27


J/ elastic and p-diss. photoproduction cross sections vs W
Elastic and proton-dissociation cross sections measured simultaneously using Regularised Unfolding Simultaneous fit to Wp distributions, taking into account correlations between elastic and p-diss. cross sections
H1 elastic J/ photoproduction H1 p-diss. J/ photoproduction

p

EPJ C73 (2013) 2466


W p = N W 0
W0= 90 GeV

( p J/ Y) [nb]

( p J/ p) [nb]

120 100 80 60 40 20 0

H1 data HE H1 data LE

=0.67 ±0.03

el

120 100 80 60 40

H1 data HE H1 data LE

=0.42 ±0.05

pd

Fit HE, LE, H1(2005)

Fit HE, LE, H1(2005)

pd / el

1.4 1.2 1 0.8 0.6 0.4 0.2

H1 J/ photoproduction

Q2 = 0.1 GeV |t| < 1.2 GeV2

2

20 0 40 60

Q2 = 0.1 GeV |t| < 8 GeV2 MY < 10 GeV

2

40

60

80 100 W p [GeV]

80 100 W p [GeV]

H1 data HE, LE, Q2 = 0.1 GeV Fit HE, LE

2

Ratio pd/
Armen Buniatyan

el

slowly decreasing with W
Results from H1 experiment

0

p

40

60

80 100 W p [GeV]

QFTHEP 2013

28


J/ elastic and p-diss. photoproduction cross sections vs t
EPJ C73 (2013) 2466

t ­momentum transfer squared at the proton vertex
H1 p-diss. J/ photoproduction

H1 elastic J/ photoproduction

d( p J/ p) [nb/GeV 2] dt

d( p J/ Y) [nb/GeV2] dt

H1 data HE

H1 data HE Fit HE, H1(03)

10

2

Fit HE, H1(03)

40
10

40
10

1 0

Q2 = 0.1 GeV2 40 GeV < W p < 110 GeV

1

Q2 = 0.1 GeV2 40 GeV < W p < 110 GeV MY < 10 GeV

0.2 0.4 0.6 0.8

1

1.2

0

2

4

6
-n

8

-t [GeV2]

-t [GeV2]

d ~e dt

- bel |t |
2

bel= 4.88 ± 0.15 GeV

d 1 + pd | t | = N pd dt n b

bpd= 1.79 ± 0.12 GeV2

b is related to the transverse size of interaction: bpd is significantly lower than bel
Armen Buniatyan Results from H1 experiment QFTHEP 2013 29


J/ elastic photoproduction cross sections vs t
EPJ C73 (2013) 2466

New H1 measurement- two energy ranges: Wp=40-110 GeV and Wp=25-80 GeV
Transition region from fixed target to previous HERA data Good agreement with previous HERA measurements Fixed target data: steeper slope, lower normalisation Extrapolation of H1 data to high W agrees with LHCb measurement
Armen Buniatyan Results from H1 experiment QFTHEP 2013 30


Conclusions
Six years after the end of data taking, H1 is an active experiment producing valuable results in a broad area of physics. New results presented: - Final measurement of inclusive NC/CC cross sections - Several new measurements of hadronic final state and particle production - Combined H1/ZEUS measurement of inclusive diffractive DIS with leading proton

HERA has a rich physics program that has to be completed !

Armen Buniatyan

Results from H1 experiment

QFTHEP 2013

31


Armen Buniatyan

Results from H1 experiment

QFTHEP 2013

32


Strangeness production in DIS: visible cross sections for K
H1prelim-13-033

0 S

and
H1prelim-13-031

Entries/MeV

1200

H1 Preliminary
1000

800

K0

S

600



p

-

Np- = 6946 ± 182

400

200

0 1.08 1.09 1.1 1.11 1.12 1.13 1.14 1.15 1.16 M (p) [GeV]

7 < Q2< 100 GeV

2

, 0.1 < y < 0.6

145< Q2< 20000 GeV2 , 0.2 < y < 0.6

+9.4 0 +0.50 vis (ep eKS X) = 10.66± 0.04(stat.)-0.53 (sys.) nb vis (ep e X ) = 144.7 ± 4.7(stat .)-8.5 (sys .) pb

Armen Buniatyan

Results from H1 experiment

QFTHEP 2013

33


Combined Inclusive Diffractive DIS Cross Sections measured with forward proton spectrometers
Proton Spectrometer data in 0.09<|t|<0.55 GeV2

first combination of H1 and ZEUS diffractive data !

Armen Buniatyan

Results from H1 experiment

QFTHEP 2013

34


Diffractive Jet Photoproduction with a Leading Proton
2006-2007 data, integrated luminosity 30pb-1 Leading proton measured in the Very Forward Spectrometer (VFPS): two stations at 218m and 222m; reconstruction efficiency >96% ; background <1% Two jets with ET>5.5 (4) GeV 0.01 2

Data unfolded to hadron level using Singular Value Decomposition of the response matrix

Armen Buniatyan

Results from H1 experiment

QFTHEP 2013

35


Diffractive Jet Photoproduction with a Leading Proton

Data suppressed in comparison with NLO QCD by factor 0.67
data/nlo=0.67

±0.04 (stat)±0.09 (sys)±0.20 (scale)±0.14(pdf)

No obvious dependence of suppression on x Large theoretical uncertainties connected with the DPDF uncertainty and scale variation

Armen Buniatyan

Results from H1 experiment

QFTHEP 2013

36