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Update on DVCS what can we do if 1 fb -1 ? S. Fazio EIC Task Force meeting BNL – May 2nd, 2013

Update on DVCS what can we do if 1 fb -1 ? S. Fazio EIC Task Force meeting BNL – May 2nd, 2013. From the EIC white paper. ~ 1 year of data taking . Simulation: y >0.01 (detector acceptance) Detector smearing The | t |-binning is (3* reso )

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Update on DVCS what can we do if 1 fb -1 ? S. Fazio EIC Task Force meeting BNL – May 2nd, 2013

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  1. Update on DVCSwhat can we do if 1 fb-1 ?S. FazioEIC Task Force meetingBNL –May 2nd, 2013

  2. From the EIC white paper ~ 1 year of data taking • Simulation: • y>0.01 (detector acceptance) • Detector smearing • The |t|-binning is (3*reso) • Exponential |t|-dependence exp(B*|t|) • B-slope=5.6 compatible with H1 data, to facilitate Dieter’s global fitting • 5% systematic uncertainties S.Fazio - EIC Task force meeting, BNL

  3. Submitted paper on DVCS at EIC arXiv:1304.0077v1 S.Fazio - EIC Task force meeting, BNL

  4. Let us consider an eRHIC with 5x100 GeV2 and 1fb-1 and lets see what changes for the error bands shown in the white paper • Statistical errors rescaled them from 10 fb-1 to 1 fb-1. • 5% systematic uncertainty and added in quadrature to the rescaled statistical uncertainty • ROOT used to do an exponential fit: A*exp(B*t) and calculate the values and errors of the normalization A and the slope B plus the correlation coefficient c. • The fitted values (A, dA, B, dB, c) are used as an input to the Markus’ GNU-plot code which computes errors using method of eigenvector distributions. • The output of the GNU-plot code is used as input to aMarkus' FORTRAN code which  computes the error bands for the cross section and the partonic distribution  using the Fourier Bessel function integral and gives tables in text format.This code, in calculating the error bars, considers the |t| range achievable experimentally and extrapolates beyond. • the text output from the Bessel code can be plotted using ROOT (my thanks to Tom for the useful PYTON example-script which easily does it). S.Fazio - EIC Task force meeting, BNL

  5. First exercise: reproducing the white paper 20x250 figures using input cards from Markus White paper Beam energy: 20x250 GeV2 10 < Q2 < 17.78 GeV2 3.98x10-3 < x < 6.31x10-3 went trough the whole exercise as in the previous slide... the white paper is reproduced! S.Fazio - EIC Task force meeting, BNL

  6. We want to study the impact of having only a low energy – low luminosity eRHIC at hand 5x100 GeV2 Beam energy: 5x100 GeV2 10 < Q2 < 17.78 GeV2 0.1 < x < 0.158 10 fb-1 if eRHIC collects 10 times less lumi: with 1 fb-1 (10 years of data taking at 1032 ?) only the |t|<0.85 GeV2 can be measured 1 fb-1 S.Fazio - EIC Task force meeting, BNL

  7. Error bands 5x100 1 fb-1 5x100 1 fb-1 ~ 10 y of data taking TO BE COMPARED WITH ~ 1 y of data taking S.Fazio - EIC Task force meeting, BNL

  8. Exponential vs dipole What ifds/dt follows a dipole dependence rather than en exponential? Can we discriminate with 1 fb-1 ? Lets try to fit a dipole parameterization and superimpose it to the data generated according to an exponential A*exp(B*|t|) We can hardly discriminate a dipole dependence with 1 fb-1. We must keep in mind that only error bars are rescaled -> play the same game simulating a small sample with 1 fb-1 to reproduce fluctuations actual fluctuations no rescaling S.Fazio - EIC Task force meeting, BNL

  9. OUTLOOK • Can we measure the asymmetries and still preserve some discriminatory power among different theoretical assumptions with 1 fb-1 ? 100 fb-1 20x250 I will ask Dieter for the code (or the parameterization of the theory curves) for AUT at 5x100 and rescale the errors for the expected uncertainty with 1 fb-1 UPDATE by next week... S.Fazio - EIC Task force meeting, BNL

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