Mila PanduroviċVinča Institute of Nuclear Sciences,Srbija

Deep inside a proton -structure functions F2 for heavy flavors

Back in the old days …

The key to inner life of proton is so-called structure function

So in order to see a most intimate life inside proton (heavy flavors) one should consider shooting the biggest available arrow

Q2 Q2

High Energy eP collisions

Neutral current Charged current

Characteristic variables

Virtuality

Bjorken scaling variable

Inelasticity

Photoproduction (p) Q2 < 1 GeV2

Low Q2 DIS : 1< Q2 < 100 GeV2

High Q2 DIS : Q2 > 100 GeV2

Kinematic regimes

2 p·qX=

Q2

Y= p·qp·k

Q2= - q2 = - (k-k’)2

Quark parton model (QPM)If the resolution with which the proton is probed is sufficiently fine ( large enough Q2 ) hadrons are viewed as being composed of a number of point-like constituents-partons

If |p|2»mp2 QPM interprets Deep

Inelastic Scattering as the elastic scattering of a e- (e+) from a single quark

The eP cross section is an incoherentsum of - individual eqi scatteringcross sections times the probability -fi(x) that quark qi is carrying fraction x of proton’s momentum

e

P

parton

e’

Inclusive DIS cross section

Inclusive NC DIS cross section of ep → eX depends on two independent kinematic variables (chosen to be) x and Q2

2πα2

xQ4 [ y2xF1 + (1-y)F2]

d2σNC

dxdQ2=

F1(x),F2(x) – proton structure functions are giving the probability fi(x)=qi(x)dx of finding a quark carrying fraction x of a proton’s momentum (weighted by the electric charge of a quark)

Deep Inelastic Scattering - DIS

F2(x)=2 ·x · F1(x)F2(x)= ei2· x·[qi(x)+ qi(x)]

i

What proton is made of …

Goal of the analysis

Measurement of the charm and beauty content in both low and high Q2 eP neutral current interactions and calculation of charm and beauty contributions F

2cc and

F2bb to the proton structure function

For this purpose the property of long lifetime of charm and beauty hadrons is exploited

Inclusive DCA Method

DCA Method is based on lifetime information of heavy hadrons – impact parameters δ~DCA are different for heavy and light quarks

DCA - Distance of Closest Approach

Tools - h1oo

H1CalcVertex

H1CentralTrack H1Selection

H1Vertex

H1CalcJet

? !

H1CentralTrack

H1SVFit

uds DJANGOcc, bb RAPGAP, CASCADEp X PHOJET

Data and MC

MONTE CARLO

All MC event samples are passed through H1 detector simulation program

DATA

CJC tracks

CST Tracks

CJC- CST track fit

CST Hits

HERA I Data

CJC tracks

CST Tracks

CJC- CST track fit

CST Hits

HERA II Data

FST tracks

Quark flavour separation

S1, S2,S3- significance of tracks with highest, second highest and

third highest absolute significance

To reduce the uncertainty due to resolution and suppress contribution from light quarks will be using “subtracted” significance distributions

ΔS=S+- S-

Signed impact parameterSignificance Error on DCA

S=

δσ(δ)

SORRY NO CAN

DO !

Adding this to CV

Plot anything please !!!H1PLOTTER

Very much Please The nicest Please

Total MC

udscb

- Data

Significance distributions

Fitting

Using the least squares simultaneous fit of the subtracted S1, S2 and S3 we are obtaining the scaling factors Pc, Pb and Pl

of the number of heavy and light quarksThe obtained fractions of heavy quarks are used to calculate the reduced cross section for interaction of heavy quarks c(b)

F2cc=cc+

y2

1+(1+y)2FLcc

Using this we obtain the structure functions for c ( or b)

NC(x,Q2)= xQ4

2·π·α [1+(1+y)2]d2σNC

dxdQ2

cc(x,Q2)= NC(x,Q2) Pc · NcMCgen

Pc · NcMCgen + Pb · Nb

MCgen+Pl · NlMCgen

BCC

SummaryStructure functions are inheritance which HERA is giving us for the future experiments

As we are going to“feed” that to LHC...

Coach : Ivanka Božoviċ-Jelisavčiċ advising: Paul Thompson, Tatsiana Klimkovich …

M. Panduroviċ, Vinča Institute of Nuclear Sciences, X talks, 18-19 october, 2007

LHC

I hope that is going to be the exact meal or …something or someone else is going to be served …