skip to main content

DOE PAGESDOE PAGES

Title: How Bright is the Proton? A Precise Determination of the Photon Parton Distribution Function

It has become apparent in recent years that it is important, notably for a range of physics studies at the Large Hadron Collider, to have accurate knowledge on the distribution of photons in the proton. We show how the photon parton distribution function (PDF) can be determined in a model-independent manner, using electron-proton (ep) scattering data, in effect viewing the ep → e + X process as an electron scattering off the photon field of the proton. To this end, we consider an imaginary, beyond the Standard Model process with a flavor changing photon-lepton vertex. We write its cross section in two ways: one in terms of proton structure functions, the other in terms of a photon distribution. Requiring their equivalence yields the photon distribution as an integral over proton structure functions. As a result of the good precision of ep data, we constrain the photon PDF at the level of 1%–2% over a wide range of momentum fractions.
Authors:
 [1] ;  [2] ;  [3] ;  [4]
  1. Univ. of California San Diego, La Jolla, CA (United States). Dept. of Physics; European Organization for Nuclear Research (CERN), Geneva (Switzerland). Theoretical Physics Dept.
  2. Istituto Nazionale di Fisica Nucleare (INFN), Milano (Italy)
  3. European Organization for Nuclear Research (CERN), Geneva (Switzerland). Theoretical Physics Dept.; National Centre for Scientific Research-Mixed Organizations (CNRS-UMR), Paris (France)
  4. European Organization for Nuclear Research (CERN), Geneva (Switzerland). Theoretical Physics Dept.; Univ. of Oxford (United Kingdom). Rudolf Peierls Centre for Theoretical Physics
Publication Date:
Grant/Contract Number:
sc0009919; 614577; 321133; 340281; NSF PHY11-25915
Type:
Published Article
Journal Name:
Physical Review Letters
Additional Journal Information:
Journal Volume: 117; Journal Issue: 24; Journal ID: ISSN 0031-9007
Publisher:
American Physical Society (APS)
Research Org:
Univ. of California, San Diego, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25); European Research Council (ERC); Simons Foundation; National Science Foundation (NSF)
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
OSTI Identifier:
1335720
Alternate Identifier(s):
OSTI ID: 1423952