A study of the energy evolution of event shape distributions and their means with the DELPHI detector at LEP

  • The DELPHI Collaboration
Original Paper

Abstract.

Infrared and collinear safe event shape distributions and their mean values are determined in \({\mathrm{e^+e^-}}\) collisions at centre-of-mass energies between 45 and 202GeV. A phenomenological analysis based on power correction models including hadron mass effects for both differential distributions and mean values is presented. Using power corrections, \(\alpha_s\) is extracted from the mean values and shapes. In an alternative approach, renormalisation group invariance (RGI) is used as an explicit constraint, leading to a consistent description of mean values without the need for sizeable power corrections. The QCD \(\beta\)-function is precisely measured using this approach. From the DELPHI data on Thrust, including data from low energy experiments, one finds
$$\beta_0 = 7.86 \pm 0.32$$
for the one loop coefficient of the \(\beta\)-function or, assuming QCD,
$$n_{\mathrm{f}} = 4.75 \pm 0.44 $$
for the number of active flavours. These values agree well with the QCD expectation of \(\beta_0=7.67\) and \(n_{\mathrm{f}}=5\). A direct measurement of the full logarithmic energy slope excludes light gluinos with a mass below 5GeV.

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References

  1. 1. D. E. Groom Eur. Phys. J. C 15, 1 (2000)Google Scholar
  2. 2. M. Beneke. Phys. Rep. 317, 1 (1999)Google Scholar
  3. 3. G. Sterman. (1998)Google Scholar
  4. 4. A. Dhar. Phys. Lett. B 128, 407 (1983)Google Scholar
  5. 5. A. Dhar and V. Gupta. Phys. Rev. D 29, 2822 (1984)Google Scholar
  6. 6. A. Dhar and V. Gupta. Pramana 21, 207 (1983)Google Scholar
  7. 7. J. G. Korner, F. Krajewski, and A. A. Pivovarov. Phys. Rev. D 63, 036001 (2001)Google Scholar
  8. 8. D.E. Soper and L.R. Surguladze. Phys. Rev. D 54, 4566 (1996)Google Scholar
  9. 9. Yu. L. Dokshitzer and B.R. Webber. hep-ph/9704298, 1997Google Scholar
  10. 10. Yu. L. Dokshitzer et.al. Nucl. Phys. B 511, 396 (1997)Google Scholar
  11. 11. Yu. L. Dokshitzer, et.al. JHEP 9805, 003 (1998)Google Scholar
  12. 12. Yu. L. Dokshitzer and B.R. Webber. Phys. Lett. B 352, 451 (1995)Google Scholar
  13. 13. D. Wicke. Nucl. Phys. Proc. Suppl.64, 27 (1998)Google Scholar
  14. 14. P. Abreu Z. Phys. C 73, 229 (1997)Google Scholar
  15. 15. K. Hamacher. Nucl. Phys. Proc. Suppl. B 54A, 34 (1997)Google Scholar
  16. 16. DELPHI Coll., P. Abreu Nucl. Instr. Meth. A 303, 233 (1991)Google Scholar
  17. 17. DELPHI Coll., P. Abreu Nucl. Instr. Meth. A 378, 57 (1996)Google Scholar
  18. 18. DELPHI Coll., P. Abreu Phys. Lett. B 456, 322 (1999)Google Scholar
  19. 19. D. Wicke. PhD thesis, BUGH Wuppertal, 1999, WU DIS 99-5Google Scholar
  20. 20. P. Abreu Nucl. Instrum. Meth. A 427, 487 (1999)Google Scholar
  21. 21. T. Sjostrand Comput. Phys. Commun. 135, 238 (2001)Google Scholar
  22. 22. DELPHI Coll., P. Abreu Z. Phys. C 73, 11 (1996)Google Scholar
  23. 23. E.L. Berger, X. Guo, and J. Qiu. Phys. Rev. D 54, 5470 (1996)Google Scholar
  24. 24. S. Brandt Phys. Lett. 15, 57 (1964)Google Scholar
  25. 25. G. Parisi. Phys. Lett. B 74, 65 (1978)Google Scholar
  26. 26. L. Clavelli. Phys. Lett. B 85, 111 (1979)Google Scholar
  27. 27. S. Catani, G. Turnock, and B. R. Webber. Phys. Lett. B 295, 269 (1992)Google Scholar
  28. 28. C.L. Basham Phys. Rev. Lett. 41, 1585 (1978)Google Scholar
  29. 29. Y. Ohnishi and H. Masuda SLAC-PUB-6560Google Scholar
  30. 30. G. P. Salam and D. Wicke. JHEP 05, 061 (2001)Google Scholar
  31. 31. Ralf Reinhardt. PhD thesis, BUGH Wuppertal, 2001, WUB-DIS 2001-6. http://elpub.bib.uni-wuppertal.de/edocs/documente/ fb08/diss2001/reinhardt/d080113.pdfGoogle Scholar
  32. 32. Yu.L. Dokshitzer. hep-ph/9911299, 1999Google Scholar
  33. 33. Yu. L. Dokshitzer, G. Marchesini, G. P. Salam. Eur. Phys. J. Direct C 03, 1 (1999)Google Scholar
  34. 34. Yu. L. Dokshitzer, G. Marchesini, and B. R. Webber. JHEP 07, 012 (1999)Google Scholar
  35. 35. S. Catani Nucl. Phys. B 407, 3 (1993)Google Scholar
  36. 36. S. Catani and B.R.Webber. JHEP 10, 005 (1997)Google Scholar
  37. 37. B. R. Webber, hep-ph/9510283Google Scholar
  38. 38. R. K. Ellis, D. A. Ross, and A. E. Terrano. Nucl. Phys B 178, 412 (1981)Google Scholar
  39. 39. CERN 89-08 Vol. 1, 1989Google Scholar
  40. 40. S. Catani and M.H. Seymour. Phys. Lett. B 378, 287 (1996)Google Scholar
  41. 41. AMY Coll., Y.K. Li Phys. Rev. D 41, 2675 (1990)Google Scholar
  42. 42. DELPHI Coll., P. Abreu Eur. Phys. J. C 14, 557 (2000)Google Scholar
  43. 43. G. Grunberg. Phys. Rev. D 29, 2315 (1984)Google Scholar
  44. 44. P. M. Stevenson. Phys. Rev. D 23, 2916 (1981)Google Scholar
  45. 45. M. Beneke. Phys. Lett. B 307, 154 (1993)Google Scholar
  46. 46. C.J. Maxwell, D.T. Barclay, M.T. Reader. Phys. Rev. D 49, 3480 (1994)Google Scholar
  47. 47. W. Celmaster and R. J. Gonzalves. Phys. Rev. D 20, 1420 (1979)Google Scholar
  48. 48. J. M. Campbell, E. W. N. Glover, C. J. Maxwell. Phys. Rev. Lett. 81, 1568 (1998)Google Scholar
  49. 49. M. Acciarri Phys. Lett. B 489, 65 (2000)Google Scholar
  50. 50. S. Bethke. J. Phys. G 26, R27 (2000)Google Scholar

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© Springer-Verlag Berlin/Heidelberg 2003

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  • The DELPHI Collaboration

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