Update on DVCSwhat can we do if 1 fb-1 ?

S. FazioEIC Task Force meetingBNL – May 2nd, 2013

S.Fazio - EIC Task force meeting, BNL 22 May 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)• 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

2 May 2013

arXiv:1304.0077v1

S.Fazio - EIC Task force meeting, BNL 42 May 2013

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 a Markus' 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 52 May 2013

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

the white paper is reproduced!

went trough the whole exercise as in the previous slide...

S.Fazio - EIC Task force meeting, BNL 62 May 2013

5x100 GeV2

We want to study the impact of having only a low energy – low luminosity eRHIC at hand

Beam energy: 5x100 GeV2

10 < Q2 < 17.78 GeV2

0.1 < x < 0.158

10 fb-1

1 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

S.Fazio - EIC Task force meeting, BNL 72 May 2013

Error bands

TO BE COMPARED WITH

5x1001 fb-1

5x1001 fb-1

~ 10 y of data taking

~ 1 y of data taking

S.Fazio - EIC Task force meeting, BNL 82 May 2013

Exponential vs dipoleWhat if ds/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|)

€

func. =A

1+ B⋅ t( )2

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 92 May 2013

Can we measure the asymmetries and still preserve some discriminatory power among different theoretical assumptions with 1 fb-1 ?

OUTLOOK

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

100 fb-1 20x250

UPDATE by next week...