May 2004

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A.Rostovtsev
Institute f. Theor. and Exp. Physics in Moscow,
DESY at Hamburg
May 2004
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(No Transcript)
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Schematic view of the H1 detector
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Kinematic plane coverage
Coverage
5 decades in x and Q2
Sensitivity to
x
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F2 measurements
Proton structure function data accurate to 2 to
3 over bulk of phase space
Extraction of NLO PDFs
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Typical systematic errors are 6
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Both e-p and ep are important
x
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• Studies of beauty and charm production using H1
  central silicon tracker (CST).
• Flavour identification using distance of closest
  approach of track to vertex d.

• Determine significance S d/s(d) for all CST
  tracks.
• Use 2 tracks with largest significance, S1 and S2
• Example, S2 distribution

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• Determine ratios

• fb 2, fc 25

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• Resulting(large acceptance, extrapolations
  small).
• First measurement, in good agreement with
  expectations from NLO calc. using H1 PDFs.

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New cross-section measurements

• Some regions of kinematic plane remain to be
  studied, particularly intermediate x at low Q2.
• Radiative events, effective reduction in
  Ee.
• Access largerfor given Q2.

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Cross-section at low Q2

• Identify ISR events without tagging g via
• Mean Eeff 15 GeV, c.f. nominal value Ee
  27.6 GeV.

• Use shifted vertex data (low Q2).
• BST and SpaCal necessary for measurement of
  scattered electron and rejection of
  photoproduction background.

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• Cross-section from H1 ISR and QED Compton data
  (final results) in good agreement.
• Measurements consistent with other data in
  regions of overlap.

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Behaviour of F2 at low x

• Can parameterise structure function as
• Extract l(Q2) by fitting F2 as function of x at
  constant Q2.
• Behaviour of l(Q2) in transition region (Q2 1
  GeV2) intriguing.
• Probing limits of perturbative QCD.
• Further investigation not possible at HERA II
  because of acceptance limitations introduced by
  new focussing magnets.

• Measurements of l(Q2)

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FL determination (H1)
Sensitivity to FL at high y (low x)
Assumptions
..at small x
Very good description
sr shape is defined by a kinematical factor
y2/Y
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Still need to improve accuracy of the data
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Measure cross section at fixed x and Q2 varying
y by changing Ep in a range from 400 GeV upwards.
From 3 to 10 pb-1 is necessary at lower Ep
Systematic errors included
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PDF extraction
PDF analysis of the data coming from a single
experiment reduces the uncertainty involved in
the combination of correlated systematic errors
from many different experiments with possible
incompatibilities.
The uncertainties from the Global (ZEUS Fix
target data) fit
This gets worse when using ZEUS data alone
mid and high x gluons especially problematic
One experiment PDF extraction is dominated by
stat. errors.
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Include Jet measurements in PDF analysis
Jets in DIS (Breit frame)
Di-jets in photoproduction (xg gt0.75)
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Jets constrain medium x gluon distribution Improve
d precision on the gluon at higher x
x
Good agreement with the Global ZEUS fit
Agreement with H1 PDFs except for a small
difference in gluon shape
MRST2001 underestimates gluon density at low x
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Fractal structure of the protons
Scaling, self-similarity and power-law behavior
are F2 properties, which also characterize
fractal objects
Serpinsky carpet
D 1.5849
Proton 2 scales
Generalized expression for unintegrated structure
function
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Limited applicability of perturbative QCD
ZEUS hep-ex/0208023
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For x lt 0.01 ? 0.35 lt Q lt 120 GeV2 c2
/ndf 0.82 !!!
With only 4 free parameters
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Summary

• HERA provides
• rich inclusive data with a 5 decades coverage in
  x and Q2 with a precision reaching up to 2.
• PDFs can be extracted from the data collected by
  a single experiment
• FL measurement made down to Q2 of 1 GeV2
• information about heavy quark content of DIS
• much more which was not covered in this report