H1 FPS + ZEUS LPS1 FPS/LPS Combination Preliminary request M.Ruspa, V. Sola, M.Kapishin, R.Polifka

H1 FPS + ZEUS LPS2 Combine H1-ZEUS diffractive cross sections with Sasha Glasov’s combination code Available samples  H1 HERA II FPS (published, [2])  ZEUS 2000 LPS (published, [3]) Goal In this talk report on combination of proton spectrometer results (LPS-FPS) [2] DESY [3] DESY

H1 FPS + ZEUS LPS3 What/how/when to combine? M. RuspaZEUS General Meeting - 30/06/20113 Combining σ r D(4) point to point not possible >> different xIP, t, Q2, beta binning >> swimming in xIP depends on t through alpha’ Averaging the t-slope possible but needs time >> significant discrepancy Swimming σ r D(4) in beta, Q2 and making a combined Regge fit looks the cleanest way The fit will give b, IP and IR paramenters Work in progress timescale beyond summer Combining σ r D(3) point to point possible Done, to be realeased for EPS Will focus on this in the following

H1 FPS + ZEUS LPS4 Average t-slope as a function of x IP --- Regge fit uncertainty band H1 FPS HERA II DESY H1 FPS HERA I DESY ZEUS LPS 2 DESY ─ H1 FPS HERA II Regge fit

H1 FPS + ZEUS LPS5 Average t-slope as a function of x IP, free ΔB ─/─ upper lines for ZEUS data ─/─ lower lines for H1 data ─ H1 FPS HERA II Regge fit  H1/ZEUS uncertainty band ΔB~ GeV 2  uncertainty of H1+ZEUS cross section extrapolation from |t|-range [ ] GeV 2 to |t|<1 GeV 2 Δσ/σ~ 6-8% B IP +ΔB, B IR +ΔB

H1 FPS + ZEUS LPS6 Measured in the t range [0.1 – 0.7] GeV 2 Extrapolation to t min < |t| < 1 GeV 2 with algebrical integration Available σ r D(3) measurements Measured in the t range [ ] GeV 2 Extrapolation to t min < |t| < 1 GeV 2 hidden in acceptance corr

H1 FPS + ZEUS LPS7 7  ZEUS 2000 LPS (33 pb -1 ) and H1 FPS HERA II (156 pb -1 )  Binning originally very different (fixed Mx for ZEUS, fixed beta for H1) ZEUS points swam to H1 bins  Correlated systematics from [2] (H1) and [3] (ZEUS) All systematics in [2] taken as correlated though no explicit mention in that paper  Normalization Each sample left with its normalization and related uncertainty N.B.: Bringing samples to a fixed (average) normalization makes no difference Fit ingredients t rangeNorm. unc. ZEUSNorm. unc. H1Ratio H1/ZEUS [t min -1] GeV 2 +11% -7% 6%H1 / ZEUS = 0.85 ± 0.01 (stat) ± 0.03 (syst) / (norm) [ ] GeV 2 7%4.5%H1/ZEUS = 0.91 ± 0.01 (stat) ± 0.03 (syst) (norm)

H1 FPS + ZEUS LPS8 Systematics H1 FPS hadronic energy scale electromagnetic energy scale scattered electron angle measurement energy and momentum of leading proton background subtraction reconstruction of event vertex bin centre correction x IP reweighting β reweighting Q 2 reweighting t reweighting (correlated systematics) ZEUS LPS electron position electron energy scale hadronic energy scale proton dissociation background vertex recontruction momentum of the leading proton proton position x IP reweighting t reweighting

H1 FPS + ZEUS LPS9 SGfit in the ZEUS t range fit -> χ 2 = 52 / 58 = 0.89 Fitted systematics: 1 HadEn_h ElecEn_h ElecTh_h DifBeta_h DifXpom_h DifT_h EpFPS_h PxFPS_h PyFPS_h DifQ2_h VtxEff_h Backgr_h Bcccor_h Norm_h Ehscale_zeus Eescale_zeus Pdiss_zeus xIPweight_zeus Tweight_zeus Norm_zeus

H1 FPS + ZEUS LPS10 Pull distributions 10

H1 FPS + ZEUS LPS11 Gain in Precision M. RuspaZEUS General Meeting - 30/06/ Q2 beta xIP xsec_fit err_fit (%) xsec_h1 err_h1 (%) err_fit/err_h

H1 FPS + ZEUS LPS12 Second analysis – full t range 12 R.Polifka

H1 FPS + ZEUS LPS13 H1 FPS HERA II data Averaged method: DA / Elec y av = y e 2 +y da ∙(1-y da ) → Q av 2,x av x IP = 1 – E p /920 β= x / x IP for x IP >0.01 → β-dependence at fixed Q 2,x IP → β does not depend on M x scale β = Q 2 /(Q 2 +M x 2 ) for x IP <0.01 M X = 1.10∙ M x had ∙√ y av /y had E had → E had (1±Δ), M x →M x √(1±Δ) H1 LAr scale dependence

H1 FPS + ZEUS LPS14 SGfit/WA Nominal H1 Had escale taken out from error grid  H1 Had escale partially responsible of raise towards low x IP ( and ) N.B.: when taking out Had escale, SGfit highest beta and lowest x IP

H1 FPS + ZEUS LPS15 How to deal with the Lar shift  Use as default the observed shifts HadEn_H ElecEn_H Olaf Behnke: use values from the inclusive combination to estimate a procedural uncertainty related to the energy scales h8H_caleLar h3EeLar Overall effect ~ 1%, up to 5% for the lowest x IP bins  Take the LAr escale uncertainty as uncorrelated between H1 data points - the correlation between the first two x IP bins and the rest is minimal - in the first two x IP bins the uncertainty swaps from negative to positive in different β and Q 2 bins, i.e. the reaction of the cross section to the energy shift is different Decided to consider the latter as procedural uncertainty

H1 FPS + ZEUS LPS16 Olaf Proposal

H1 FPS + ZEUS LPS17 Ratio nominal case to case with H1 hadronic escale taken as uncorrelated H1 LAr hadronic escale taken as uncorrelated

H1 FPS + ZEUS LPS18 Procedural Uncertainties M. RuspaZEUS General Meeting - 30/06/ ZEUS Swimming factors  Average effect ~ 1% Additive VS Multiplicative Only normalization uncertainties taken as multiplicative while all other uncertainties treated as additive (see slide 19)  Average effect ~ 4.3% Correlations between H1 and ZEUS Similar systematic uncertainties identified >> electromagnetic energy scale >> background subtraction >> x IP reweighting >> t reweighting  Average effect ~ 2 % H1 hadronic energy scale not correlated between H1 data points

H1 FPS + ZEUS LPS19 Procedural Uncertainties M. Ruspa19ZEUS General Meeting - 30/06/2011 Ratio nominal case to case with all uncertainties except normalization taken as additive

H1 FPS + ZEUS LPS20 Procedural Uncertainties Ratio nominal case to case with all correlations ZEUS-H1 taken together

H1 FPS + ZEUS LPS21 Q 2 = 2.5 GeV x IP = β = Including single points (not matching with other experiments) does not change the fit results (nor the χ 2 nor the systematic shifts) but allow to obtain a wider kinematical coverage → do not changed χ2 in the combination fit 121 H1 points 58→106 ZEUS points 169 H1+ZEUS combined points Additional ZEUS LPS points

H1 FPS + ZEUS LPS22 Plots for EPS 2011

H1 FPS + ZEUS LPS23 Plots for EPS 2011

H1 FPS + ZEUS LPS24 Plots for EPS 2011

H1 FPS + ZEUS LPS25 Summary & Outlook Fit to σ r D(3 LPS-FPS in the ZEUS t-range [ GeV 2 ] ready - combined cross section plots vs x IP, Q 2 - pull distributions - procedural uncertainties - second analysis Following plots to be realeased for EPS, zoomed plots will be prepared for H1ZEUS plenary Combined Regge fit to LPS-FPS data on the way

H1 FPS + ZEUS LPS26 Backup: H1 E had scale shift for x IP <0.01 x IP = x IP = log 10 β Linear Y scale H1 FPS log 10 β-bin limits: -3.0, -2.5, -2.0, -1.5, -1.0, -0.5, 0.0 E had -7% → MC hadron energy scale shifted at -1.75δ relative to default MC for 2 lower x IP bins β = Q 2 / (Q 2 + M x 2 )

H1 FPS + ZEUS LPS27 Backup: H1 E had scale shift for x IP <0.01 x IP = x IP = log 10 β LogY scale H1 FPS log 10 β - bin limits: -3.0, -2.5, -2.0, -1.5, -1.0, -0.5, 0.0 E had -7% → MC hadron energy scale shifted at -1.75δ relative to default MC for 2 lower x IP bins