Measurements of the proton structure at HERA and their impact for LHC

Recent results on proton structure functions from H1 and ZEUS Collaborations are presented. The data have been recorded in ep and e−p collisions for both Neutral Current and Charged Current reactions, covering a wide kinematic range of squared four-momentum transfers Q2, from 0.2GeV2 to 30000GeV2, and Bjorken x between ∼5 ∗ 10−6 and 0.65. Data from both experiments have been combined, leading to significantly reduced experimental uncertainties. The combined measurements are analysed in a NLO QCD fit, and a set of parton density functions, HERAPDF1.0, is extracted from these data alone. New direct measurements of the structure function FL, making use of dedicated low energy runs of the HERA machine, are also presented. The impact of the HERA data on the parton density functions and predictions for LHC is discussed. 1. Measurements of the structure function F2 A new measurement [1] of deep inelastic lepton-proton scattering (DIS) is based on data collected by the H1 collaboration in the year 2000 with positrons of energy Ee=27.6GeV and protons of energy Ep=920GeV, corresponding to a centre-of-mass energy √ s=319GeV. The measurement is performed in the kinematic region of 12GeV2 ≤ Q2 ≤ 150GeV2 and of 10−4 ≤ x ≤ 0.1. The luminosity amounts to 22 pb−1. This measurement is combined with similar H1 data taken in 1996/97 at Ep=820GeV [2]. The combined data represent the most precise measurement in the presented kinematic domain with total uncertainties typically in the range of 1.3-2%. The data are used to determine the structure function F2(x, Q2), which is observed to rise continuously towards low x at fixed Q2. A NLO QCD analysis is performed to obtain a new set of parton distribution functions H1PDF2009 [1] from the inclusive DIS cross section measurements presented here as well as from previously published H1 measurements at low [3] and high [2] Q2. The data and the NLO QCD fit from H1 data alone are shown in Figure 1. 2. Combined H1 and ZEUS measurements A combination [4] is presented of the inclusive DIS cross sections measured by the H1 and ZEUS Collab∗Speaker on behalf of H1 and ZEUS Collaborations Email address: [email protected] (Alexey Petrukhin) H1PDF 2009 H1 Data 2 H1 Low Q 2 H1 High Q x -4 10 -3 10 -2 10 -1 10 0 0.5 1 1.5 2 = 150 GeV 2 Q -4 10 -3 10 -2 10 -1 10 0 0.5 1 1.5 2 = 120 GeV 2 Q x -4 10 -3 10 -2 10 -1 10 0 0.5 1 1.5 2 = 90 GeV 2 Q -4 10 -3 10 -2 10 -1 10 0 0.5 1 1.5 2 = 60 GeV 2 Q -4 10 -3 10 -2 10 -1 10 0 0.5 1 1.5 2 = 45 GeV 2 Q -4 10 -3 10 -2 10 -1 10 0 0.5 1 1.5 2 = 35 GeV 2 Q -4 10 -3 10 -2 10 -1 10 0 0.5 1 1.5 2 = 25 GeV 2 Q -4 10 -3 10 -2 10 -1 10 0 0.5 1 1.5 2 = 20 GeV 2 Q -4 10 -3 10 -2 10 -1 10 0 0.5 1 1.5 2 = 15 GeV 2 Q -4 10 -3 10 -2 10 -1 10 0 0.5 1 1.5 2 = 12 GeV 2 Q H1 Collaboration