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QCD Studies with resurrected JADE Data Stefan Kluth Moriond QCD '03 1
QCD Studies with resurrected JADE Data
Stefan Kluth
for M. Blumenstengel, P. A. Movilla Fernandez, S. Bethke,O. Biebel, C. Pahl, J. Schieck
Max-Planck-Institut für PhysikFöhringer Ring 6D-80805 Mü[email protected]
Outline:1 Introduction2 Data vs modern MCs
3 Scaled Momentum ξ=ln(1/x)4 Extended Power Correction Fits
QCD Studies with resurrected JADE Data Stefan Kluth Moriond QCD '03 2
1 Why low energy e+e− data?
Running strong coupling:
αS(Q) = α
S(µ)/(1+2β
0ln(Q/µ))
�
C
�
= Acα
S(Q) + B
Cα
S
2(Q) + PC/Q
�
Interplay between hard and softQCD best studied at 'medium'energies
�
JADE data!
Eur. Phys. J. C22 (2001) 1-15
QCD Studies with resurrected JADE Data Stefan Kluth Moriond QCD '03 3
1 The JADE Detector and Data
JADE @ PETRA/DESY 1979 - 1986
�
s = 12 to 46,8 GeV
QCD Studies with resurrected JADE Data Stefan Kluth Moriond QCD '03 4
1 The JADE Software
Detector simulation (pre-GEANT) and reconstructionrunning on IBM RS6000 AIXsystem
�
generate physics usingmodern generators, e.g.PYTHIA, HERWIG,ARIADNE (LEP 1 tunes)�
pass through JADEsimulation/recontruction�
compare with data orderive corrections
Hadronic event in JADE at 35 GeV
P.A. Movilla Fernandez, PhD Thesis,RWTH Aachen, PITHA 03/01
QCD Studies with resurrected JADE Data Stefan Kluth Moriond QCD '03 5
2 Background from b-productionPYTHIA b-event at 14 GeV
Subtract b-background (~9%), present data at udsc hadron-level
P.A. Movilla Fernandez, PhD Thesis,RWTH Aachen, PITHA 03/01
QCD Studies with resurrected JADE Data Stefan Kluth Moriond QCD '03 6
2 JADE Data vs MC: ThrustGenerators: PYTHIA 5.7, HERWIG 5.9, ARIADNE 4.08, COJETS 6.23 with OPAL (-based) LEP 1 tunes, JETSET 6.3 with JADE tuneData at hadron-level corrected for bb-background
P.A. Movilla Fernandez, PhD Thesis,RWTH Aachen, PITHA 03/01
QCD Studies with resurrected JADE Data Stefan Kluth Moriond QCD '03 7
2 JADE Data vs MC: y23
(Durham)
PYTHIA/ARIADNE generally ok, HERWIG too hard at low
�
s, JETSET6.3(J) ok too, COJETS fails at low
�
sP.A. Movilla Fernandez, PhD Thesis,RWTH Aachen, PITHA 03/01
QCD Studies with resurrected JADE Data Stefan Kluth Moriond QCD '03 8
3 Scaled momentum ξ = ln(1/x)
Shape of ξ=ln(1/x) distribution around peak: skewed Gaussian MLLA (Q
0
� Λ) calculation for partons
�
LPHD
�
hadron spectra
Nucl. Phys. B355 (1991) 54
σ: width, S: skewness, k: kurtosis, ξ0: peak position
D � �
N y2 � � y
exp k y8
�
S y �
2
�
2 � k y � 2
4� S y � 3
6
� k y � 4
24
� � � � � y � y , y � log s2
eff
, � 0 � � �
11 � 2n f
932C A
, � � F y � O 1
S � � � � 3 � 3, k � � � � 4 � 4 � 3
QCD Studies with resurrected JADE Data Stefan Kluth Moriond QCD '03 9
3 Measurements and Fits
Fit MLLA (Fong/Webber): Λeff
, N, and <ξ>, O(1) or ξ0
�
results for Λeff
, N stable w.r.t. <ξ>, O(1) or ξ0
M. Blumenstengel, PhD Thesis, RWTH Aachen
QCD Studies with resurrected JADE Data Stefan Kluth Moriond QCD '03 10
3 Peak Fit Results
Peak position <ξ> or ξ0 and Ndepend on √s
Λeff
and O(1) constant
M. Blumenstengel, PhD Thesis, RWTH Aachen
s GeV � 0 N �
effMeV
22 2.74 � 0.09 11.6 � 0.4 136 � 2835 3.06 � 0.05 14.1 � 0.2 142 � 2544 3.19 � 0.06 16.4 � 0.6 110 � 38
QCD Studies with resurrected JADE Data Stefan Kluth Moriond QCD '03 11
3 MLLA Peak Position Fits
Λeff
= 206
�
3 MeV
Reasonable description of data(similar result from OPAL)
M. Blumenstengel, PhD Thesis, RWTH Aachen
� 0 y �
12
y � Cy � C
y � log s2 �
eff
QCD Studies with resurrected JADE Data Stefan Kluth Moriond QCD '03 12
3 Flavour (Mass) Effects
M. Blumenstengel, PhD Thesis, RWTH Aachen
�
c , b0 � �
uds0 � 0.5 log
�c , b
�
uds
Fit with Λb, Λ
c and Λ
uds with
data from OPAL for ξ0
b, ξ0
c
and ξ0
uds as constraints
�
uds184 � 33MeV
�
c239 � 90MeV
�
b247 � 28MeV
Mass effects about 20 � 30%
QCD Studies with resurrected JADE Data Stefan Kluth Moriond QCD '03 13
4 Extended Power Correction FitsDMW model:
�
assume integrable αS at very low Q
�
analyse renormalon ambiguities
y Dy
1 � T 2
M H2 1
C 3 �
BT ln 1
�
BT
�
DBTBT , �
S
BW12
ln 1
�
BW
�
DBWBW , �
S
y � y PT Dy P
d �
dy
�
d �
PT
dyy � Dy P
P M
I
Q
�
0
I
� �
S
R
�
0
I
� 1
I0
�
I �
S k dk
Nucl. Phys. B469 (1996) 93
QCD Studies with resurrected JADE Data Stefan Kluth Moriond QCD '03 14
4 Extended Fits with BW
pQCD is O(αS
2)+NLLA,
�
s<MZ
χ2(pQCD+DMW) = 65.5/24
χ2(pQCD+DMW+A11
) = 22.2/23
Evidence for additional terms, probably behaving like ln(Q)/Q
P.A. Movilla Fernandez, PhD Thesis,RWTH Aachen, PITHA 03/01
QCD Studies with resurrected JADE Data Stefan Kluth Moriond QCD '03 15
4 Extended Fits with y23
(D)pQCD is O(α
S
2)+NLLA
�
extended fit ranges
�
DMW prediction is
�
y23
�
~ ln(Q)/Q2
χ2(pQCD) = 151/107
χ2(pQCD+A20
/Q2) = 71.2/106
Evidence for additional terms, probably behaving like 1/Q2
at low
�
s
Analysis with restricted fit rangesis consistent too
P.A. Movilla Fernandez, PhD Thesis,RWTH Aachen, PITHA 03/01
QCD Studies with resurrected JADE Data Stefan Kluth Moriond QCD '03 16
Summary
� Modern MC generators with LEP 1 tunes generally agree with JADE data down to 14 GeV
� Quantitative QCD studies at 14 to 44 GeV
� Ideal laboratory for interplay hard � soft QCD
� Measured ξ=ln(1/x) 22 to 44 GeV with JADE
� Test MLLA QCD predictions (together with OPAL)
� Study flavour (mass) effects (together with OPAL)
� Extended DMW power corrections fits
� BW additional A
11ln(Q)/Q contribution?
� y23
(D) additional A20
/Q2 contribution?