inelastic j/ y differential cross sections: paper material

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Inelastic J/y differential cross sections: paper material

A. Bertolin, R. Brugnera

Outline:• short introduction

• differential pt2

cross section in z bins

• differential z cross section in pt bins

• y(2S) to J/y cross sections ratio• momentum flow along the J/y direction (new)• outlook

ZEUS week 15-17 Feb. 2012

DESY, 15/2/2012

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previous ZEUS papers:

1. Measurement of inelastic J/y photoproduction at HERA DESY 97-147 (July 1997) Zeitschrift f. Physik C76 (1997) 4, 599-612 Alessandro B. PhD thesis + Riccardo B. 94 data

2. Measurements of inelastic J/y and y^prime photoproduction at HERA DESY-02-163 (September 2002)Europ. Phys. Journal C 27 (2003) 173-188 Alessandro B. + Riccardo B. 96-97 data

3. Measurement of Inelastic J/y Production in Deep Inelastic Scattering at HERADESY-05-071 (May 2005)European Physical Journal C44 (2005) 13-25Alessandro B. + Alexei A. + Igor K. (+ Leonid G. + Riccardo B.) 96-00 data

4. Measurement of J/y helicity distributions in inelastic photoproduction at HERADESY-09-077 (June 2009)JHEP12 (2009) 007Alessandro B. + Riccardo B. HERA I + HERA II

short introduction

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paper material

as already stated several times we have to take into account several external constraints: we are in 2012, myself and Riccardo have other commitments ...

so we have to define some realistic goals for this paper:

• ds / dpt2 in z slices: shown as preliminary in DIS11, all mature PHP experiments have

measured it

• ds / dz in pt slices: inelasticity, z, is a key variable for J/y production

provide to the theorists an inelasticity distribution at “high p t”

• y(2S) to J/y cross section ratio: needed to evaluate the y(2S) ® J/y p p feed down

• study of the momentum flow (using vertex tracks) along / against the J/y direction of flight: theorists are telling us that this measurements is very significant, never done before in PHP

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96/97 pos. data (20718 27889)

mbtake & GLOMU effic.: ok

num97v5.2 HERWIG MC

evtake + mbtake lumi: 38.0 pb-1

98/99 ele. data (30758 32906 )


num98v5.0 HERWIG MC


99/00 pos. data (33125 37715 )


num98v5.0 HERWIG MC


03/04 pos. data (45783 51245)


num03t6.0 HERWIG MC


04/05 ele. data (52258 57123 )


num05t3.0 HERWIG MC


06 ele. data (58207 59947)


num06t4.0 HERWIG MC available


06/07 pos. data before L/MERs (60005 62639)mbtake & GLOMU effic: oknum07t4.1 HERWIG MC availableevtake + mbtake lumi: 137.5 pb-1S (HERA I) = 114.1 pb-1

S (HERA II) = 354.2 pb-1

S (all HERA) = 468.3 pb-1

MC samples produced runlib v2008a.2

last version available

w.r.t. v2007a.2 used previously some

changes occurs for HERA II but the

overall sum stays 354.2 pb-1

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HERWIG MC J/y (direct photon)

HERWIG MC y(2S) (direct photon)

PYTHIA MC J/y (resolved photon)

PYTHIA MC c ® J/y g (resolved photon)

EPSOFT MC J/y

DIPSI MC: muon chamber efficiency in MC

GRAPE MC: muon chamber efficiency in MC

http://www-zeus.desy.de/~bertolin/ZEUS_ONLY/epstapes.html

http://www-zeus.desy.de/~bertolin/ZEUS_ONLY/effictapes.html

http://www-zeus.desy.de/~bertolin/ZEUS_ONLY/resolvedtapes.html

http://www-zeus.desy.de/~bertolin/ZEUS_ONLY/psitapes.html

MC samples produced

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EPSOFT MC vs data

generated parameters:

• Wep / f.f. = Wgp flat

• MX taken from EPSOFT MC of the form (1 / Mx)

• exp (-b pt2), sample with b=0.5 and sample with b=1, mixed with the same weight

only reweighting:

• reweighted to a liner dependence Wgp dependence (Wep / 60)

to compare EPSOFT MC and data:• 60 < W < 240 GeV (as for the nominal analysis)

• 0.9 < z < 1 (0.1 < z < 0.9 for the nominal analysis)

• pt > 0 GeV (pt > 1 GeV for the nominal analysis)

• 2 (vertex) tracks (³ 3 (vertex) tracks for the nominal analysis)

• E(FCAL) > 1 GeV (as for the nominal analysis)

• HERA I + HERA II data

proton diffractive

dissociation is dominant

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EPSOFT MC vs data

S/B huge

data to MC ratio for W consistent with being flat (A1 consistent with 0)

in the diffractive modeling part of the sys. errors will take care of this little mismatch in pt pt

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EPSOFT MC vs data

in the diffractive modeling part of the sys. errors will vary the (1 / MX) dependence and hence the Efcal

EPSOFT MC shape

decay track reaching the m chambers

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HERWIG MC

based on our past experience the only observable which needs attention is the p t – pt2

distribution

effect on the acceptances is mild, NOT a touchy issue

reweight the HERWIG MC to bring the simulation closer to the data

selected phase space for the reweighing procedure:• 60 < W < 240 GeV (as in the nominal analysis)

• 0.3 < z < 0.9 (avoid 0.1 < z < 0.3 where the signal is small and the non resonant background is large)

• pt > 1 GeV (as for the nominal analysis)

• ³ 5 (vertex) tracks (³ 3 in the nominal analysis)

• E(FACL) > 1 GeV (as for the signal)

• HERA I + HERA II data

proton diffractive

dissociation is negligible

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HERWIG MC

pt2 reweighting procedure: fit the reconstructed dN/dpt

2 in both data and MC with a suitable function, F(pt

2), weight: ratio of the data to MC function, Fdata (pt2)/FMC (pt

2)

F is arbitrary as long as it describes data and MC

F = A0 + S Am cos(mw pt2) + S Bm cos(mw

pt2)

may be this is not the best possible choice ...

F = P1*(exp(P2*pt2)+P3*exp(P4*pt

2))P2: first slopeP4: second slopeP3: relative weight

04 ele. / 05 data

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HERWIG MC

96 / 97 98 / 99 99 / 00 03 / 04 04 / 05 06 06 / 07 96 / 97 98 / 99 99 / 00 03 / 04 04 / 05 06 06 / 07

parameters are remarkably stable vs time

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Proton diffractive dissociation subtraction

diffractive events are generated at z » 1we measure the cross section for z < 0.9the overlap should be ZEROHOWEVER due to the finite z resolution some of the diffractive events are RECONSTRUCTED with z < 0.9

EPSOFT MC generated z

fit the reconstructed z distribution to estimate the amount of diffractive events left after the z < 0.9 cut

for the fit the only change with respect to the nominal analysis is done for the z range:• from 0.1 < z < 0.9• to 0.3 < z < 1

we:• remove 0.1 < z < 0.3 because there is no diffractive yield at low z, instead observe larger

non resonant background and expect contributions also from beauty and may be resolved• we add 0.9 < z < 1 to have more diffractive background and hence more “signal” for the fit

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data

HERWIG MC

EPSOFT MC

even

ts /

bin

shape distorted by the E(FCAL) > 1 GeV and ³ 3 (vertex) tracks requirements

purpose of the fit: fractions of HERWIG MC and EPSOFT MC that best describe the data

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even

ts fr

actio

n / b

in

HERWIG MC component

from fit

MC sumdata

outcome: HERWIG MC fraction for z < 0.9 is 93.9 %

data: stat. errors, MC: sys. errors, due for example to the hadronic energy resolution, with size comparable to the data stat. errors, NOT shown in the above plot

in the range 0.3 < z < 0.9, this fit, the result is: 0.9397566

in the nominal analysis z range, 0.1 < z < 0.9, the result is: 0.9397768

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• 60 < W < 240 GeV• 0.3 < z < 0.9• pt > 1 GeV

• ³ 3 (vertex) tracks• E(FACL) > 1 GeV• HERA I + HERA II data

even

ts fr

actio

n / b

inControl plots for the MC mixture

EPSOFT MC

HERWIG and EPSOFT MC predictions are affected by (systematic) uncertainties due, for example, to the hadronic energy reconstruction NOT shown in these plots

even if not too large these uncertainties are of the size of the data stat. errors (HERA I + HERA II data)

in the signal part of the sys. error the W and pt HERWIG MC spectra and the hadronic energy resolution implemented in the MC, E-Pz(rec)-E-Pz(gen), will be varied accordingly

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even

ts fr

actio

n / b

inControl plots for the MC mixture

the uncertainty on the muon chamber efficiency is not shown for the MC histograms, its size is

similar to the data statistical error, this uncertainty will be

included in the signal part of the sys. error

EPSOFT MC

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0.75 < z < 0.9 0.6 < z < 0.75

0.45 < z < 0.6 0.3 < z < 0.45

Alessandro: black

Riccardo: blue

60 < W < 240 GeV

1 < pt2 < 100 GeV2

Cross section vs pt2 in z slices

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0.1 < z < 0.3 Alessandro: black

Riccardo: blue

two analyses are in very good agreement

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Cross section vs z in pt slices

1 < pt < 2 GeV 2 < pt < 3 GeV

3 < pt < 4.5 GeV pt > 4.5 GeV

60 < W < 240 GeV

0.9

0.90.9

0.9

Alessandro: black

Riccardo: blue


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2S to 1S cross section ratio

basic formulas:

with some algebra:

FULL details:http://www-zeus.desy.de/~bertolin/ZEUS_ONLY/zn-03004/node41.htmlZEUS Note of the HERA I paper

for the HERA I paper we used PDG2002:Data Br1SMu/5.88E-2/,Br2SMu/0.70E-2/,Br2S1S/55.7E-2/in PDG2010:Data Br1SMu/5.93E-2/,Br2SMu/0.77E-2/,Br2S1S/59.5E-2/

in today’s presentation PDG2010 values are being used

PDG2010 ≡Please use this CITATION: K. Nakamura et al. (Particle Data Group), Journal of Physics G37, 075021 (2010) and 2011 partial update for the 2012 edition.

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2S to 1S cross section ratio vs z


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2S to 1S cross section ratio vs pt


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2S to 1S cross section ratio vs W


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p flow against / along the J/y direction

• 60 < W < 240 GeV

• pt > 1 GeV

• 0.3 < z < 0.9 (0.1 < z < 0.3 removed because of the small amount of signal expected and large amount non resonant background observed)

• ³ 3 (central) vertex tracks• E(FCAL) > 1 GeV

J/y direction of flight in the lab.

• vertex tracks

• pt(min) > 150 MeV

• | h | < 1.75• do not consider the m+ and m- tracks• track and J/y same hemisphere: p projection along

the J/y gives a positive contribution to Palong• track and J/y opposite hemisphere: p projection

along the J/y gives a positive contribution to Pagainst

as discussed with F. Maltoni (UC Louvain, Be)

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goal: check if the Color Singlet Model, as implemented in the LO + PS HERWIG MC, can give a reasonable description of the energy flow along the J/y direction

the against direction is studies only “as a cross check”

reminder:• in the CSM you have only a J/y and a backward “hard” gluon (transverse momentum

conservation in PHP) … so along we expect almost nothing• in the Color Octet Model you have a J/y with some nearby hadronic activity (“soft” gluons)

and a backward “hard” gluon … some along activity should be visible

• clearly such an analysis would profit of large J/y pt (like in CMS) but theorist told us than a qualitative results in PHP would be very valuable anyway

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• have to measure two distributions: Pagainst and Palong

binning of each distribution: 0. 0.25 0.5 1. 1.5 2. 2.5 3. 4. 5. GeV

• have to measure vs pt(J/y)

pt(J/y) bins: 1. 1.4 1.9 2.4 3.4 4.2 10. GeV (bins used for the “inelastic J/y helicity paper”)

expect large statistical errors (like in the helicity paper)

Alessandro’s analysis:

(1) fit a number of J/y events for every pt(J/y) bin (6 invariant mass fits only)

(2) compute Pagainst / Palong distribution for events close to the J/y mass peak

(3) compute Pagainst / Palong distribution for events in the side bands

(4) knowing the background below the peak normalize properly the side bands contribution for Pagainst / Palong

(5) subtract (2) and (4) to get Pagainst / Palong for J/y events only

(6) build Pagainst / Palong for every pt(J/y) bin using MC: add HERWIG (94 %) and EPSOFT (6 %) MC predictions

(6) compare data and MC predictions both with normalization set to 1.

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Riccardo’s analysis:

(1) build an invariant mass distribution for every pt(J/y) bin, 1. 1.4 1.9 2.4 3.4 4.2 10. , and for every p flow bin, 0. 0.25 0.5 1. 1.5 2. 2.5 3. 4. 5. , i.e. 6 x 9 distributions for Palong and 6 x 9 distributions for Pagainst

(2) fit them all to get Pagainst / Palong for J/y events only

(3) build Pagainst / Palong for every pt(J/y) bin using MC: add HERWIG (94 %) and EPSOFT (6 %) MC predictions

(4) compare data and MC predictions both with normalization set to 1.

every method has its own advantages and disadvantages, both have been used in the past … side band subtraction method has been for the inelastic J/y helicity paper

how does the two methods compare ?


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p flow against the J/y: data comparison

two analyses are in very good agreement for the Pagainst distribution

Alessandro: black

Riccardo: blue

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p flow along the J/y: data comparison

two analyses are in very good agreement for the Palong distribution

Alessandro: black

Riccardo: blue

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p flow along / against the J/y: MC comparison

along against

Alessandro: black

Riccardo: pink


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p flow along / against the J/y: MC comparison

along against


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p flow against the J/y

crosses: HERA I + HERA II data, stat. errors only

continuous line: HERWIG MC, CMS only

the HERWIG MC provides a reasonable description of the data

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p flow along the J/y

crosses: HERA I + HERA II data, stat. errors only

continuous line: HERWIG MC, LO CMS + PS

the HERWIG MC provides a reasonable description of the data moreover the agreement improves as the J/y pt increases

momentum flow around the J/y does not show large deviations from the CMS picture

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Observation on cross sections

• proton diffractive dissociation background is subtracted. This is fundamental for the theorists;

• y(2S) feed down is not subtracted, an inclusive reconstruction of the y(2S) decay would be needed and we do not have it. But the 2S to 1S cross section ratios vs p t W and z are measured. Theorists (should) know how to correct for this. Moreover they never asked us to perform this subtraction;

• J/y from any B hadron decay are not subtracted:

• the ratio between B hadron to J/y to J/y from primary vertex is much smaller at HERA than at hadron colliders (CDF, D0, CMS, ATLAS)

• theorists never asked us to perform this subtraction

• no PHP experiment up to now has performed this subtraction

• a subtraction based on data is very hard

• the only subtraction we could do would be fully based on MC … likely the theorists could account for this better than us (by adding a beauty component to the QCD predictions)

• the cross section we quote, the number in nb, is corrected for this effect, as explained in the following slides

• we will quantify the size of this contribution

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for cross section vs pt2 in z slices

for every Dpt2 bin:

• disregarding any difference in the correction factors for beauty:

s = N / CH L f.f. BR Dpt2 = s0

• taking explicitly the beauty correction factor into account:

s = N – Nb / CH L f.f. BR Dpt2 + Nb / Cb L f.f. BR Dpt

2

…

s = s0 [1+(Nb/N)(CH-Cb)/Cb]

J/y from b decay: effect of the quoted number of nb

outcome:

• if Nb/N << 1 s = s0

• if CH=Cb s = s0

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continuous: 0.1 < z < 0.3

dashed: 0.3 < z < 0.45

dotted: 0.45 < z < 0.6

z > 0.6: at the event level negligible

usually < 10 events, 16 at most (low z low pt)

expected number of J/y from b decay (Pythia PHP inclusive beauty sample):

when Nb is largest Nb/N < 16/375 < 0.045

usually Nb/N < 10/400 < 0.025

total number of beauty MC events processed:

22.207.433

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0.3 < z < 0.45:

CH=Cb s = s0

whatever amount of beauty we have in data the number in nb we quote for the cross section is correct

0.1 < z < 0.3:

s = s0 [1+(Nb/N)(CH-Cb)/Cb]

= s0 [1+ 0.25×(Nb/N)]

= s0 [1+ 0.25×0.045]

< s0 [1+ 1.2 %]


negligible cross section increase (stat. error is > 10 % level)

for z > 0.45 Nb/N is so small that the effect is negligible anyway

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outcome:

beauty is included in the cross section and the quoted cross section, the number of nb, takes this contribution properly into account

any theorist can compute the J/y cross section, according to his preferred model, compute the J/y from beauty contribution, according to his preferred model, add the two numbers and compare with our data

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2S to 1S cross section ratios

naive expectation of the LO CS model: flat ratios at 0.25(2) according to the latest PDG values

most of the central values are above 0.25, mild indications that the z ratio may not be flat

LO CMS prediction:s µ Gmm / m3

1S: 3096.6 MeV, 5.93 % x 92.9 keV2S: 3686.0 MeV, 0.77 % x 304 keV

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Conclusions and outlook

the material for the paper has been presented … we have the feeling this is the best we can do keeping in mind the different constraints we have (we are not leaving in a word with an infinite amount of money and time)

last but not least:

• the computation of the systematic errors will have to be carried out

• a paper draft will be prepared

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extra slides

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luminosities tuning plots:• high z (z > 0.9): EPSOFT MC tuning• medium z (z < 0.8): HERWIG MC tuning diffractive fit:• E(FCAL) only• >= 3 tracks cross section vs pt2 cross section vs z 2S to 1S ratio

/!\ check latest .for p flow along and against

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ff*BR*Lumi_tot=0.0975*0.0593*468300• ff for 60 < W < 240 GeV and Q2

max=1 GeV2

• BR = ( 5.93 ± 0.06 ) × 10−2

• Lumi_tot = 468.3 pb-1 = 468300 nb-1

PDG read on 27/1/2012Please use this CITATION: K. Nakamura et al. (Particle Data Group), Journal of Physics G37, 075021 (2010) and 2011 partial update for the 2012 edition.

BR(2S) = ( 7.7 ± 0.8 ) × 10−3

BR(2S to 1S+anything) = ( 59.5 ± 0.8 ) × 10−2

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default values in mmumufit.kumac

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96/97 pos. data

num97v5.3 = num97v5.2 SL5 compliant

HERWIG MC: 74P717

beauty MC: 7KP717 (num97t5.2 ) 98/99 ele. data


HERWIG MC: 82E819

beauty MC: none 99/00 pos. data


HERWIG MC: 82P020

beauty MC: 8JP020, summary ok

03/04 pos. data

num03t6.0

HERWIG MC: CNZ324 (50 k), CNZ424 (50 k), CNU424 (50 k), CN4Z24 (25 k)

beauty MC: none 04/05 ele. data

num05t3.0

HERWIG MC: DSBF25

beauty MC: DSNE25, summary ok 06 ele. data

num06t4.0

HERWIG MC: ETRE26

beauty MC: ETRE26 06/07 pos. data before L/MERsnum07t4.1HERWIG MC: FIX627beauty MC: FIX627, summary ok

list of up to date funnel versions as of 15-11-2011

Beauty MC processing

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Old slide

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Current status

inelastic j/ y differential cross sections: paper material

Documents

mbtake glomu effic

herwig mcevtake mbtake

jy productionprovide

photon epsoft mc jy

jy cross section ratio

photonpythia mc c jy

mcgrape mc

jy direction of flight