global qcd analysis of parton structur

7/28/2019 Global QCD Analysis of Parton Structur

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http://arxiv.org/abs/hep-ph/9903282v3


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[49] Wu-Ki Tung, Proceedings of 5th International Workshop on Deep Inelastic

Scattering and QCD (DIS 97), Chicago (1997), hep-ph/9706480.

[50] M. Gluck, E. Reya and A. Vogt, Zeit. Phys. C67 (1995) 433.

[51] S. Kretzer and I. Schienbein, Phys. Rev. D58, (1998) 94035, hep-ph/9805233

[52] J. Amundson, C. Schmidt, W.K. Tung, and X.N. Wang, to be published.

[53] M. Cacciari and M. Greco, Nucl. Phys. B421, (1994) 530, hep-ph/9311260.

[54] C. Balazs and C.P. Yuan, Phys. Rev. D56, (1997) 5558, hep-ph/9704258.

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100 101 102 103 104

1/X

100

101

102

Q(GeV)

DIS (fixed target)HERA (94)DYW-asymmetryDirect-Jets

Figure 1 Kinematic map of the (x,Q) range covered by the data sets used in

CTEQ global analysis. The complementary roles of the fixed-target, HERA, and

Tevatron experiments are clearly seen.

x

0

0.2

0.4

0.6

0.8

1

1.2

xf(x,Q

)

10-4 10-3 10-2 10-1 .2 .3 .4 .5 .6 .7

Q = 5 GeV

.8

Gluon / 15dbarubarscuvdv(dbar-ubar) * 5

Figure 2 Overview of CTEQ5M parton distributions at Q = 5 GeV. The gluon

distribution is scaled down by a factor of 15, and the ( d u) distribution is scaled

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up by a factor of 5.

x

0.5

1

1.5

2

dbar

/ubar

10-2 10-1 .2 .3

Q = 5 GeV

cteq4mcteq5m

Figure 3 Comparison of the (d/u) distribution in CTEQ4M and CTEQ5M. The

major change is due to the new E866 data. Cf. Fig. 7

x

0

0.01

0.02

0.03

0.04

0.05

x*(dbar-

ubar

)

10-4 10-3 10-2 10-1 .2 .3 .4 .5 .6 .7

Q = 5 GeV

.8

cteq4mcteq5m

26

Figure 4 Comparison of the (d u) distribution in CTEQ4M and CTEQ5M. The

sharp drop-off around x = 0.2 of the CTEQ5 curve is due to the new E866 data,

Cf. Fig. 7. Behavior above x = 0.3 is mostly due to extrapolation of the adopted

parametrization, since there are very little experimental constraints on sea quarks

in this region.

0.2 0.4 0.6

x

0.7

0.8

0.9

1

NMC F2d / 2 F2

p

CTEQ5MNMC Expt.

Figure 5 Comparison of the NMC Fd2 /Fp2 data (integrated over Q) with NLO

QCD results based on CTEQ5M.

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0.5 1 1.5 2

Y

-0.1

0

0.1

CDFW-leptonAsymmetry

CTEQ5MCDF data

Figure 6 Comparison of the CDF W-lepton asymmetry data, as a function of the

rapidity y, with NLO QCD results based on CTEQ5M.

0.1 0.2 0.3

x2

0.7

0.8

0.9

1

1.1

1.2

pd/2pp

Drell-Yan Cross-section Ratio

E866CTEQ5M

Figure 7 Comparison of the E866 dp

/pp

data, as a function ofx2, with NLOQCD results based on CTEQ5M.

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x

0

0.2

0.4

0.6

0.8

1

Glu/x-1.5/

(1-x)3.0

10-4 10-3 10-2 10-1 .2 .3 .4 .5 .6 .7

Q = 80 GeV

Q = 5 GeV

Q = 2 GeV

CTEQ4M.Q2CTEQ5M.Q2CTEQ4M.Q5CTEQ5M.Q5CTEQ4M.Q8CTEQ5M.Q8

Figure 8 Comparison of the gluon distributions from CTEQ4M and CTEQ5M at

three energy scales: 2, 5, and 80 GeV. Note the effect of QCD evolution.

100 200 300 400

pT (GeV)

0

0.2

0.4

0.6

0.8

1

1.2

1.4

Incl. Jet : pt7 * d/dpt

Error bars: statistical only

8% < Corr. Sys. Err. < 30%

Ratio: Data / NLO QCD (CTEQ5M | CTEQ5HJ)

2 = norm. factor :

CTEQ5HJ: 25/24 1.08CTEQ5M : 24/24 1.04

D0

(10-14 nb GeV6)

Data / CTEQ5MCTEQ5HJ / CTEQ5MD0 dataCTEQ5HJCTEQ5M

Figure 9 Comparison of D0 inclusive jet production data to the CTEQ5 fits. Thebottom plot shows the measured cross-section d/dpt, multiplied by p7t in order to

allow a linear display. The top plot shows the ratio of the measured cross-section

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to that calculated with CTEQ5M, as well as the ratios of CTEQ5HJ to CTEQ5M.

50 100 150 200 250 300 350 400

pT (GeV)

0

0.2

0.4

0.6

0.8

1

1.2

1.4

Incl. Jet : pt7 * d/dpt

(Error bars: statistical only)

14% < Corr. Sys. Err. < 27%

Ratio: Prel. data / NLO QCD (CTEQ5M | CTEQ5HJ)

norm. facor :CTEQ5HJ: 1.04CTEQ5M : 1.00

CDF

(10-14 nb GeV6)

Data / CTEQ5MCTEQ5HJ / CTEQ5MCDF Data ( Prel. )CTEQ5HJCTEQ5M

Figure 10 Same as Fig.9 except for the CDF data.

4.5 5 5.5 6

PT (GeV)

2

4

6

8

(scale: = pT / 2 ; no kT applied)

(10-5 pb GeV5)WA70: pt

7 * E d3/d3pt (y=0)

WA70NLO QCD (CTEQ5M)

Figure 11 Comparison of the WA70 direct photon data with NLO QCD calcula-

tions using CTEQ5M. A normalization factor of 1.08 has been applied.

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4 5 6 7 8 9 10

Pt (GeV)

0

2

4

6

(from diff. measurement)kT = 1.2 -- 1.3 GeV applied

scale = pT/2

(10-6 pb GeV5)E706 Direct Photon pt

7 * E d3/d3pt

E706-530GeVE706-800GeVNLO QCD (CTEQ5M)

Figure 12 Comparison of the E706 direct photon data with NLO QCD calcu-

lations using CTEQ5M. An initial state parton kT broadening effect has been

applied, as described in the text.

x

0

0.2

0.4

0.6

0.8

1

x1.5(1

-x)-2*

g(x,Q

)

10-4 10-3 10-2 10-1 .2 .3 .4 .5 .6 .7

Q = 80 GeV

Q = 5 GeV

Q = 2 GeV

CTEQ5M-Q2CTEQ5HJ-Q2CTEQ5M-Q5CTEQ5HJ-Q5CTEQ5M-Q8CTEQ5HJ-Q8

Figure 13 Comparison of the gluon distributions from CTEQ5M and CTEQ5HJ

at three energy scales: 2, 5, and 80 GeV. Note the effect of QCD evolution. The

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dip at x 0.5 of the dashed curve is not physically significant: it is the result of

the parametrization (being the product of two factors, one rising and one falling).

Only the general magnitude of the curve in this region is meaningful.

100 200 300 400

PT (GeV)

0.6

0.8

1

1.2

1.4 Data / NLO-QCD (CTEQ5HJ)

Comparison of CDF and D0 inclusive jet d / dpT

(8 - 30 % systematic error not shown)

CDF * 1.04D0 * 1.08

Figure 14 Ratio of CDF and D0 inclusive jet cross-sections to the NLO QCDcalculation using CTEQ5HJ. This parton set also provides a better description of

the di-jet cross-sections from both experiments than the more conventional parton

sets.

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x

0

0.5

1

1.5

x*f(x,Q)

10-4 10-3 10-2 10-1 .2 .3 .4 .5 .6 .7

at Q = 5 GeV

.8

Comparison of CTEQ5M and CTEQ5HQ distributions

u

ds

G/15

c

CTEQ5M

CTEQ5HQ

Figure 15 Comparison of the parton distributions of CTEQ5HQ, defined in the

on-mass-shell ACOT scheme for heavy quarks, with those of CTEQ5M, which uses

the conventional zero-mass approximation.

10-4 10-3 10-2

x

0

0.2

0.4

0.6

F2c(

x,Q

)

Open pts: ZeusSolid pts: H1Q

2

GeV2

121212454545

10-4 10-3 10-20

0.2

0.4

0.6

F2c(

x,Q

)

Open pts: Zeus

Solid pts: H1 Q2

GeV2

77252525

Figure 16 Comparison of preliminary HERA measurement of Fc2 with order sACOT scheme calculation using CTEQ5HQ.

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x

0

0.5

1

1.5

x*f(x,Q)

10-4 10-3 10-2 10-1 .2 .3 .4 .5 .6 .7

at Q = 5 GeV

.8

Comparison of CTEQ5HQ and MRS98-1 distributions

u

d

s

G/15

c

CTEQ5HQ

MRS98-1

Figure 17 Comparison of parton distributions from MRST, in the on-mass-shell

charm scheme of Ref. [41], with those from CTEQ5HQ, at 5 GeV.

x

0

0.005

0.01

0.015

10-4 10-3 10-2 10-1 .2 .3 .4 .5 .6 .7 .8

at Q = 5 GeV

c(x,Q) * x1.5 * (1-x) -3Charm distribution comparison:

CTEQ5HQMRS98-1

Figure 18 Comparison of the charm distributions from MRST with those fromCTEQ5HQ at 5 GeV. The difference is explained in the text.

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x

0

0.2

0.4

0.6

10-4 10-3 10-2 10-1 .2 .3 .4 .5

Q = 5 GeV

Comparison of CTEQ5 and MRS98 gluon distributions

G(x,Q) * x1.5 / (1-x)2

MRS98-2MRS98-1MRS98-3CTEQ5MCTEQ5HJ

Figure 19 Comparison of the gluon distributions from MRST with those from

CTEQ5HQ at 5 GeV. The differences are explained in the text.

100 200 300 400

pT (GeV)

0.2

0.4

0.6

0.8D0 data compared to NLO-QCD (EKS) -- MRST & CTEQ5 PDFs

Inclusive jet : pt7 * d/dpt

(No normalization factors are applied)(Rsep = 1.3)

(10-14 nb GeV6)

CTEQ5HJCTEQ5MD0 DataMRST-2MRST-1MRST-3

Figure 20 Comparison of the D0 inclusive jet data with NLO QCD calculationsusing MRST and CTEQ5 distributions. All normalization factors are set to one

in this comparison.

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50 100 150 200 250 300 350 400

pT (GeV)

0.2

0.4

0.6

0.8CDF data compared to NLO-QCD (EKS) -- MRST & CTEQ5 PDFs

Inclusive jet : pt7 * d/dpt

(No normalization factors are applied)( Rsep = 1.3 )

(10-14 nb GeV6)

CTEQ5HJCTEQ5MCDF (Prel.)MRST-2MRST-1MRST-3

Figure 21 Comparison of the CDF inclusive jet data with NLO QCD calculations

using MRST and CTEQ5 distributions. All normalization factors are set to one

in this comparison.

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global qcd analysis of parton structur

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