c c ➝ j/ y g

cc J/➝ y g

ϒ

y’

cc1

cc2cc0

Hermine K. Wöhri, CERN

CMS

CMS

LHCb

Quarkonium production in pp at LHC

8th Vienna Central European Seminar 25 – 27 Nov. 2011, Vienna, Austria

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λθ

CDF Run II data: prompt J/yPRL 99, 132001 (2007)

NRQCD factorization: prompt J/y Braaten, Kniehl, Lee, PRD62, 094005 (2000)

NLO colour-singlet: direct J/yHaberzettl, Lansberg, PRL100, 032006 (2008)

LOcolour singlet

NRQCD (colour singlet+ colour octet)

pT [GeV/c]

CDF

In 1995, CDF observed J/y and y’ direct production cross sections ~50 times larger than expectations from leading-order colour-singlet production

NRQCD (including colour-octet terms) described the measured cross section… by freely adjusting long distance matrix elements

NLO CSM also able to describe cross sections but no theory able to reproduce the polarization data

@1.96 TeV

Quarkonium production puzzles: theory

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Quarkonium polarization puzzles: Tevatron experimentsCDF Run ICDF Run II

Helicity frame

CDF II vs CDF I ➝ not known what

caused the change

•

CDF vs D0 ➝ unlikely that the

different rapidity ranges can justify the discrepancy...

•

J/ψ, pp √s = 1.96 TeV

|y| < 0.4 |y| < 0.6

PRL 85, 2886 (2000)PRL 99, 132001 (2007)

0 10 20

- 0 .8

- 0 .6

- 0 .4

- 0 .2

0 .0

0 .2

0 .4

pT [GeV/c]

|y| < 1.8 |y| < 0.6

CDF Run IID0 Run II

(1S), pp √s = 1.96 TeV

Helicity frame PreliminaryPRL 101, 182004 (2008)

_

_

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Exotic quarkonium puzzles: CDF vs Belle

CDF observed a structure in B+ (➝ J/y f) K+

decays on the basis of 115 ± 12 B+ (in 6 fb-1)

M = 4143.4 +2.9-3.0 ± 0.6 MeV and

G = 15.3 +10.4-6.1 ± 2.5 MeV

19±6 events CDF

X(4140) J/➝ y f with J/y ➝ mm and f K➝ +K-

BELLE could not confirm this state ➝ set an upper limit for s·BR(X):

in contradiction to the CDF result

➝ Does the X(4140) really exist???

[PRL 102 (2009) 242002]and arXiv:1101.6058

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Quarkonium spectroscopy challenges

CDF

1P2P

• States identified in analogy to the hydrogen atom: Y(1S), Y(2S), Y(3S), cb0,1,2(1P), cb0,1,2(2P), etc

• Radially excited states, 1P, 2P, not well measured, but of equal importance for • a proper understanding of QCD at work… • feed-down into nS states (30 – 40 %)

[similar for charmonium]

cb Y(1S)➝ gwith Y(1S) ➝ mm

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The LHC achievements seen with a critical eye

The next slides give a “guided tour” through many quarkonium measurements presently available from the LHC experiments

Detailed comparisons probe their compatibility or disclose new puzzles, an important check… given the past mutually contradictory results

J/y fraction from B decays7

J/y mesons are copiously produced inB J/➝ y X decays… a background for studies of quarkonium production

“Prompt” and “non-prompt” J/y mesons areseparated through the “lifetime” dimension

[pseudo-proper decay length]

lJ/y [mm]

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The beauty feed-down shows a strong pT dependence with saturation for pT > 50 GeV/c

The mid-rapidity data points seem to show a similar trend for √s = 1.96 and 7 TeVbut the (very precise) CMS measurements sit systematically higher than those of CDF

J/y fraction from B decays vs. pT

ATLAS: arXiv:1104.3038CMS: arXiv:1111.1557

looks good

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For a given pT, the most mid-rapidity CMS data show a rather different B-fractionthan the most forward LHCb data

J/y fraction from B decays vs. pT and rapidityCMS: arXiv:1111.1557LHCb: EPJ C71 (2011) 1645

looks good

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For a given pT, the most mid-rapidity CMS data show a rather different B-fractionthan the most forward LHCb data

J/y fraction from B decays vs. pT and rapidityCMS: arXiv:1111.1557LHCb: EPJ C71 (2011) 1645

looks good

Prompt J/y pT distributions from LHCb11

LHCb published very accurate measurements, in 5 rapidity bins, up to pT ~ 15 GeV

The shape of the pT distributionscan be reproduced by the function

LHCb: EPJ C71 (2011) 16455.2 pb-1

Prompt J/y pT distributions from LHCb and ATLAS12

Also ATLAS presented very detailed measurements, extending to higher pT values

LHCb published very accurate measurements, in 5 rapidity bins, up to pT ~ 15 GeV

The shape of the pT distributionscan be reproduced by the function

LHCb: EPJ C71 (2011) 1645ATLAS: arXiv:1104.3038

ATLAS 2.27 pb-1ATLAS 2.3 pb-1 LHCb 5.2 pb-1

looks good

Prompt J/y pT shape vs. rapidity13

<pT2> clearly increases from forward to central rapidity

b = 3.69

Good agreement between the LHC experiments

looks good

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Prompt J/y pT distributions from ATLAS, CMS and LHCb


• Thanks to the high luminosity at LHC the current prompt J/y spectra extend from pT = 0 already up to 70 GeV/c, spanning 6 orders of magnitude

• The ATLAS and recent CMS data agree extremely well over the full pT range

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16





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LHCb: EPJ C71 (2011) 1645ATLAS: arXiv:1104.338CMS: arXiv:1111.1557


• The ATLAS and recent CMS data agree extremely well over the full pT range• Good agreement also with the forward ATLAS, CMS and LHCb data

looks good

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Prompt J/y pT distributions from ATLAS, CMS and LHCb• Thanks to the high luminosity at LHC the current prompt J/y spectra extend from pT = 0

already up to 70 GeV/c, spanning 6 orders of magnitude• The ATLAS and recent CMS data agree extremely well over the full pT range • Good agreement also with the forward ATLAS, CMS and LHCb data

LHCb: EPJ C71 (2011) 1645ATLAS: arXiv:1104.338CMS: arXiv:1111.1557

looks good

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Inclusive y’ from LHCb

y’ ➝ mmy’ J/➝ y pp

LHCb measured the pT differential inclusive y’ cross section in two decay channels:

11k in y’ J/➝ y pp

90k in y’ ➝ mm

LHCb-CONF-2011-026

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Prompt y’ from CMS• CMS measured the y’ inclusive, non-prompt and prompt pT differential cross-section• Prompt production cross-section allows for direct comparison with theory (no feed-down)• B-fraction as large for y’ as for J/y: for pT > 20 GeV/c, more than 50% come from B decays

arXiv:1111.1557

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Prompt y’ to J/y s·BR ratio

• The y’ to J/y cross-section ratio increases with pT

• CDF measured a systematically higher ratio

[PRD80 (2009) 031103 (R)]

[arXiv:1111.1557]It is puzzling to see that CDF measures a significantly higher ratio

The higher the collision energy the smaller should be the difference between the y’ and J/y cross sections

Is this a naïve expectation?

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Prompt y’ to J/y s·BR ratio

• The y’ to J/y cross-section ratio increases with pT

• CDF measured a systematically higher ratio

[PRD80 (2009) 031103 (R)]

[arXiv:1111.1557]It is puzzling to see that CDF measures a significantly higher ratio

Could it be that the CDF result is too high because of a luminosity bias (2s)?

The J/y and y’ data were collected in different runs; the luminosities do not cancel…

puzzling

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Inclusive y’ to J/y s·BR ratio

• Do we also see differences between CMS and LHCb?CMS: arXiv:1111.1557LHCb: EPJ C71 (2011) 1645 (J/y) LHCb-CONF-2011-026 (y’)

No significant difference between the CMS ratios and the most mid-rapidity LHCb resultDeserves a second look on the basis of the higher-statistics 2011 data

Note that these are inclusive ratios and thatthe B-fraction changes (slightly) with rapidity

To be redone with prompt ratios…

ϒ(1S) pT distributions from CMS and LHCb24

Also the bottomonium states are now available from more than one LHC experiment

CMS: PRD 83 (2011) 112004LHCb: CMS-CONF-2011-016

looks good

ϒ(1S): 〈 pT2 〉 vs. rapidity

• The <pT2> decreases at forward rapidities

• It is much larger than for the J/y

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b = 3.0

Quarkonia 〈 pT2 〉 vs. rapidity

• While the <pT2> is very different from J/y to Y, the average transverse kinetic energies are

much closer and show similar trends versus rapidity

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ϒ(1S) rapidityGood compatibility between LHCb and CMS for the ds/dy 1S production cross section

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looks good

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fdir=0.5

F. Maltoni

ϒ(1S) data-theory comparison

LHCb

CMS

The NLO colour singlet model describes the Y(1S) pT differential cross sections, of CMS and of LHCb

The NRQCD model is equally successful !

looks good

First measurement of the cc2 / cc1 cross-section ratio29

to be further improved with the higher-statistics 2011 data

[LHCb-CONF-2011-020]

LHCb reported a first measurement of thecc2 / cc1 cross-section ratio…

The measurement disagrees with NLO NRQCD…

Even only using 2010 data, LHCb already has amore detailed measurement than CDF

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LHCb

Also the cb already made a first appearance !CDF measured large feed-down contributions from the cb states to the Y(1S):cb(1P) Y(1S) = 27.1 ± 6.9 ± 4.4 % ➝cb(2P) Y(1S) = 10.5 ± 4.4 ± 1.4 % ➝for Y(1S) with |y| < 0.7 and pT > 8 GeV/c

[PRL 84 (2000) 2094]

M(cb(1P)) – M(Y(1S)) = 0.44 GeVM(cb(2P)) – M(Y(1S)) = 0.80 GeV

cb(2P) ?

cb(1P)CDF

Another look at cc production

CMS has a very good mass resolution (better than 10 MeV)thanks to a (very challenging) photon conversion measurement

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cc0

cc1

cc2

CMS

cc J/➝ y g

Tomography of the CMS inner detectorswith photon conversions

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Prospects for 2011 data analysis

All results shown in this presentation were based on the 2010 data

Much larger event samples have been acquired in 2011

Good perspectives for many more measurements

More potential physics analyses than available people…

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Quarkonium production at the LHC

All quarkonium measurements performed so far at the LHC are very consistent among the several experiments

good perspectives for major advances in our understanding of quarkonia➝

… the fun has started !and the best is still to come

➝ for an appetizer on polarization see talk by Valentin Knünz

c c ➝ j/ y g

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