- Email: [email protected]
Too much beauty …
ELSEVIER
Nuclear Physics B (Proc. Suppl.) 126 (2004) 161-164
SUPPLEMENTS
Too Much Beauty . . . F. Kapusta”’ “LPNHE
t
CNRS/IN2P3
UniversiGs P6 and P7, Paris, France
Heavy quark production is briefly reviewed in 77, 7~ and pp collisions. A simple toy model is used to comment on the treatment of the different scales. The observed discrepancy between data and theory is discussed and some hints to a solution are given.
1. b and 1.1.
c facts
in yy,
yp and
order of 13 pb f 30 % with systematical errors of the same order as the statistical ones.
pjj
yy
Concerning b and c production in yy collisions we have the L3 facts [l]. The direct and resolved components shown in fig. 1 are of the same order at LEP2 energies [2].
Figure 1. Direct and single resolved processes
D* tagging is used for extracting the open charm cross section. With muon and electron semileptonic decays, a global fit gives both open c and open b cross sections. The corresponding results are shown on the right in fig. 2. All these facts are shared by the LEP community, as summarized in the same figure. ae’e---teie-c’X N 1000 pb f 10 % while ~~~~~~~~~~~~~ is of the *I would like to thank Giulia for a financial support without which I could not have attended the Conference. tN. Arteaga, C. Carimalo and W. Da Silva : thanks for fruitful discussions. 0920-5632/s - see front matter doi:lO. 1016~j.nuclphysbps.2003.1
0 2004 Published 1.027
by Elsevier
R.V
Figure 2. L3 c and b results and world summary
Semileptonic decays give another powerful tool. Looking at the transverse momentum distribution of the muon relative to the closest jet, it looks
I? Kupustu/Nuclear
162
Physics B (Proc. Suppl.) 126 (2004) 161-164
b cross section at HERA
difficult for c quarks to mimic the b contribution, even without using a signed impact parameter. Two distinct kinematical regions, roughly around m,/2 for the charm and mb/2 for the beauty can be seen in fig. 3.
I L3
m -._ --“_
Data (preliminary) fit result udsc contribution bkg(ee+qq,n,WW,eerr)
~~
+ bkg
IO
c- Ph? 0
4
JJ
I
I
1
IO
I IO2
Q2 (GeV2) Figure 4. HERA b production
Figure 3. Transverse momentum ative to the closest jet
1.2. “lp HERA results The measured data over theory GeV2 this ratio
of the muon rel-
[4] are summarized in fig. 4. b cross section is presented as a ratio depending on Q2. Below 1 ranges from 2 to 3.
1.3. p@ B+ inclusive production at the TeVatron has seen recent improvements in its theoretical description [5], especially in the fragmentation function domain as shown in fig.5. 2. The experimentalist
summary
Figure 5. CDF B+ inclusive production
yy Physics with PYTHIA : SaS parameterizations (a la FKP), Phase Space slicing at the LO, massless versus massive quarks, all scales taken into account, acceptance corrections, effective fragmentation and simulation of the signal.
toolkit
Keeping two photon physics in mind, the experimentalist tools are :
The ten years old Drees, Kramer, Zerwas computation [2].
Zunft,
I’? Kupusta/Nuclenu
Physics
B (Pwc.
3. A toy model A simple toy model using different scales at LO can be revived [3] to quantify b and c basic total cross section properties. Using an effective parton density :
(1) a simplified
direct term
SuppI.)
126 (2004)
163
161-164
Taking a c mass of 1.55 GeV, a b mass of 4.9 GeV and using a=0.05, we can mimic the GRV LEPII DKZZ [2] prediction with X = 1.75. In fig. 6, )\ was waried between 1.6 and 1.9 to show the single resolved contribution sensitivity to a pdf. A naive increase of beauty gives an excess of charm. 4. Hints
towards
a solution
?
e+e--+e+e-qg gdirect
Various possibilities arise : play with fragmentation functions ( you can just do it within PYTHIA), fit pdf to LEP and HERA data, improve calculations with masses and different scales, add new processes... Recent theoretical computations are getting closer but still with no success, while many good reviews at International Conferences have appeared,
and similarly for the single resolved term
5. Missing
(2) where SO= 4(mi + &,) and pus is taken to be 0.6 GeV in agreement with SaSlD. After convolution total cross-section writes :
where b = 33 - 2Nflavor.
components
Some contributions are missing and need to be evaluated. yy -+ gg through the box diagram, as a tri3ute to B. De Tollis : all the physics lies in the box.
Figure 7. b production
Figure 6. Toy Model: direct and single resolved contributions for b and c
?
through the box diagram
The yy + 4q connection [6-S]. Some phase space contribution with a low central tranfer is not taken into account already at the LO.
E KapustalNuclear
164
Physics
B (Proc.
yg + 4q and gg -+ 4q have to be considered.
Figure 8. Four quark production
The ^~“l -+ 2 quarks 2 leptons background has to be estimated too, and in a more general way 2 lepton QED corrections to the total yy cross section.
-I
4 9 i 1
Figure 9. Two quarks and two leptons production
6. Conclusions A new measurement of open beauty production with real photon collisions is needed... maybe soon at SLAC with the Low Energy Photon Collider [lo]. And wait a bit for an open top cros section measurement at the future Photon Linear Collider.
Suppl.)
126 (2004)
161-164
REFERENCES 1. M. Acciari et al. (L3 Collab.), Phys. Lett. B 514 (2001) 19. M. Acciari et al. (L3 Collab.), Phys. Lett. B 503 (2001) 10. 2. M. Drees, M. KrBmer, J. Zunft and P.M. Zerwas, Phys. Lett. B 306 (1993) 371. 3. F. Kapusta, IXth International Workshop on Photon-Photon Collisions Proceedings, World Scientific (1992) 142. 4. D.H. Saxon, GLAS-PPE/2003-01. 5. P. Nason, hep-ph/0301003. 6. N. Arteaga, C. Carimalo, W. Da Silva, F. Kapusta, Photon2001 Proceedings. 7. J. Chjrla, hep-ph/0111469. 8. A. Szczurek, hep-phf0203050. 9. J. Chyla, JHEPO3 (2003) 42. 10. J. Gronberg’s talk, these proceedings.
Nuclear Physics B (Proc. Suppl.) 126 (2004) 161-164
SUPPLEMENTS
Too Much Beauty . . . F. Kapusta”’ “LPNHE
t
CNRS/IN2P3
UniversiGs P6 and P7, Paris, France
Heavy quark production is briefly reviewed in 77, 7~ and pp collisions. A simple toy model is used to comment on the treatment of the different scales. The observed discrepancy between data and theory is discussed and some hints to a solution are given.
1. b and 1.1.
c facts
in yy,
yp and
order of 13 pb f 30 % with systematical errors of the same order as the statistical ones.
pjj
yy
Concerning b and c production in yy collisions we have the L3 facts [l]. The direct and resolved components shown in fig. 1 are of the same order at LEP2 energies [2].
Figure 1. Direct and single resolved processes
D* tagging is used for extracting the open charm cross section. With muon and electron semileptonic decays, a global fit gives both open c and open b cross sections. The corresponding results are shown on the right in fig. 2. All these facts are shared by the LEP community, as summarized in the same figure. ae’e---teie-c’X N 1000 pb f 10 % while ~~~~~~~~~~~~~ is of the *I would like to thank Giulia for a financial support without which I could not have attended the Conference. tN. Arteaga, C. Carimalo and W. Da Silva : thanks for fruitful discussions. 0920-5632/s - see front matter doi:lO. 1016~j.nuclphysbps.2003.1
0 2004 Published 1.027
by Elsevier
R.V
Figure 2. L3 c and b results and world summary
Semileptonic decays give another powerful tool. Looking at the transverse momentum distribution of the muon relative to the closest jet, it looks
I? Kupustu/Nuclear
162
Physics B (Proc. Suppl.) 126 (2004) 161-164
b cross section at HERA
difficult for c quarks to mimic the b contribution, even without using a signed impact parameter. Two distinct kinematical regions, roughly around m,/2 for the charm and mb/2 for the beauty can be seen in fig. 3.
I L3
m -._ --“_
Data (preliminary) fit result udsc contribution bkg(ee+qq,n,WW,eerr)
~~
+ bkg
IO
c- Ph? 0
4
JJ
I
I
1
IO
I IO2
Q2 (GeV2) Figure 4. HERA b production
Figure 3. Transverse momentum ative to the closest jet
1.2. “lp HERA results The measured data over theory GeV2 this ratio
of the muon rel-
[4] are summarized in fig. 4. b cross section is presented as a ratio depending on Q2. Below 1 ranges from 2 to 3.
1.3. p@ B+ inclusive production at the TeVatron has seen recent improvements in its theoretical description [5], especially in the fragmentation function domain as shown in fig.5. 2. The experimentalist
summary
Figure 5. CDF B+ inclusive production
yy Physics with PYTHIA : SaS parameterizations (a la FKP), Phase Space slicing at the LO, massless versus massive quarks, all scales taken into account, acceptance corrections, effective fragmentation and simulation of the signal.
toolkit
Keeping two photon physics in mind, the experimentalist tools are :
The ten years old Drees, Kramer, Zerwas computation [2].
Zunft,
I’? Kupusta/Nuclenu
Physics
B (Pwc.
3. A toy model A simple toy model using different scales at LO can be revived [3] to quantify b and c basic total cross section properties. Using an effective parton density :
(1) a simplified
direct term
SuppI.)
126 (2004)
163
161-164
Taking a c mass of 1.55 GeV, a b mass of 4.9 GeV and using a=0.05, we can mimic the GRV LEPII DKZZ [2] prediction with X = 1.75. In fig. 6, )\ was waried between 1.6 and 1.9 to show the single resolved contribution sensitivity to a pdf. A naive increase of beauty gives an excess of charm. 4. Hints
towards
a solution
?
e+e--+e+e-qg gdirect
Various possibilities arise : play with fragmentation functions ( you can just do it within PYTHIA), fit pdf to LEP and HERA data, improve calculations with masses and different scales, add new processes... Recent theoretical computations are getting closer but still with no success, while many good reviews at International Conferences have appeared,
and similarly for the single resolved term
5. Missing
(2) where SO= 4(mi + &,) and pus is taken to be 0.6 GeV in agreement with SaSlD. After convolution total cross-section writes :
where b = 33 - 2Nflavor.
components
Some contributions are missing and need to be evaluated. yy -+ gg through the box diagram, as a tri3ute to B. De Tollis : all the physics lies in the box.
Figure 7. b production
Figure 6. Toy Model: direct and single resolved contributions for b and c
?
through the box diagram
The yy + 4q connection [6-S]. Some phase space contribution with a low central tranfer is not taken into account already at the LO.
E KapustalNuclear
164
Physics
B (Proc.
yg + 4q and gg -+ 4q have to be considered.
Figure 8. Four quark production
The ^~“l -+ 2 quarks 2 leptons background has to be estimated too, and in a more general way 2 lepton QED corrections to the total yy cross section.
-I
4 9 i 1
Figure 9. Two quarks and two leptons production
6. Conclusions A new measurement of open beauty production with real photon collisions is needed... maybe soon at SLAC with the Low Energy Photon Collider [lo]. And wait a bit for an open top cros section measurement at the future Photon Linear Collider.
Suppl.)
126 (2004)
161-164
REFERENCES 1. M. Acciari et al. (L3 Collab.), Phys. Lett. B 514 (2001) 19. M. Acciari et al. (L3 Collab.), Phys. Lett. B 503 (2001) 10. 2. M. Drees, M. KrBmer, J. Zunft and P.M. Zerwas, Phys. Lett. B 306 (1993) 371. 3. F. Kapusta, IXth International Workshop on Photon-Photon Collisions Proceedings, World Scientific (1992) 142. 4. D.H. Saxon, GLAS-PPE/2003-01. 5. P. Nason, hep-ph/0301003. 6. N. Arteaga, C. Carimalo, W. Da Silva, F. Kapusta, Photon2001 Proceedings. 7. J. Chjrla, hep-ph/0111469. 8. A. Szczurek, hep-phf0203050. 9. J. Chyla, JHEPO3 (2003) 42. 10. J. Gronberg’s talk, these proceedings.