NLO WG

** NLO** **W**orking **G**roup

established in January, 2000

established in January, 2000

A collaboration of people from the Atlas-Japan
group and the Minami-Tateya
group , for developing **NLO (Next-to-Leading Order)**
Monte Carlo event generators for high energy **hadron-collision
experiments** , for example, those at FNAL Tevatron and
CERN LHC
.

Goal

To establish an

Activities

**GR@PPA**(**GR**ace**A**t**P**roton-**P**roton/**A**nti-proton collisions): a**GRACE**-based event generator framework for hadron collisions. The program can be embedded in a general purpose event generators PYTHIA and HERWIG . Some event generators, still at the tree level (leading order), have been developed in this framework.**Automatic****NLO event-generator generation**: in principle, using the GRACE system, we can automatically calculate NLO matrix elements by adding**new vertices, propagators and external legs for corrections arising from higher-order loop diagrams**. A suitable extention is also necessary in the diagram generation part of the GRACE system. In addition, in the application to hadron collisions where*Q*-dependent parton distribution functions (PDFs) are adopted, we have to solve the**double-counting problem**of additional parton emission.**NLL (Next-to-Leading Log) initial-state****parton shower**: presently available initial-state parton shower simulations are all based upon the LL (Leading Log) approximation. We want to go beyond it!

Publications

- Simulation of Z boson p(T) spectrum at Tevatron by leading-order event generators, S. Odaka, Mod. Phys. Lett. A 25, 3047 (2010); arXiv:0907.5056 [hep-ph]
- NLO-QCD event generators in GRACE, Y. Kurihara, Acta Phys. Polon. B39, 1655 (2008)
- Initial-state parton shower kinematics for NLO event generators, S. Odaka and Y. Kurihara, Eur. Phys. J. C 51, 867 (2007); hep-ph/0702138
- NLO-QCD calculation in GRACE, Y. Kurihara et al., Nucl. Phys. Proc. Suppl. 157, 231 (2006)
- GR@PPA 2.7 event generator for pp/p anti-p collisions, S. Tsuno et al., Comput. Phys. Commun. 175, 665 (2006); hep-ph/0602213
*QCD Event Generators with Next-to-Leading Order Matrix Elements and Parton Showers*, Y. Kurihara*et al*.,**Nucl. Phys. B654 (2003) 301**;**hep-ph/0212216****hep-ph/0212216**

*Matching between matrix elements and parton showers using a Leading-Log subtraction method in NLO-QCD*, Y. Kurihara, in Proc. of CPP Symposium 2001, Tokyo, Nov. 27 - 30, 2001;**hep-ph/0207214**

*GR@PPA_4b: A Four Bottom Quark Production Event Generator for pp/ppbar Collisions*, S. Tsuno*et al.*,**Comput. Phys. Commun. 151 (2003) 216**;**hep-ph/0204222**; KEK Preprint 2002-7*Integration of GRACE and PYTHIA*, K. Sato*et al.*, Proc. VII International Workshop on Advanced Computing and Analysis Techniques in Physics Research (ACAT2000), eds. P.C. Bhat and M. Kasemann, AIP Conference Proceedings 583 (American Institute of Physics, Milville, New York, 2001), p. 214;**hep-ph/0104237**; KEK Preprint 2000-134

Presentations

*Introduction of GR@PPA event generator*, S. Tsuno, XVIIIth International Workshop on High Energy Physics and Quantum Field Theory (QFTHEP 2004), St. Petersburg, 17 - 23 Jun., 2004

*NLO event generator for LHC*, Y. Kurihara, Mini-Workshop on Physics Simulation for LHC, KEK, 5 - 6 Apr., 2004

*Introduction of GR@PPA event generator*, S. Tsuno, Mini-Workshop on Physics Simulation for LHC, KEK, 5 - 6 Apr., 2004

*A Strategy for the ME-PDF/PS Matching in Jet-associate Events*, S. Odaka, Mini-Workshop on Physics Simulation for LHC, KEK, 5 - 6 Apr., 2004

*Initial State Parton Evolution beyond the Leading Logarithmic Order of QCD*, H. Tanaka (presented by Y. Kurihara), Minami-Tateya QCD Meeting, KEK, 13 - 14 Nov., 2003*Requirements to Event Generators*, S. Odaka, Minami-Tateya QCD Meeting, KEK, 13 - 14 Nov., 2003

*NLO calculation in GRACE*, Y. Kurihara, Workshop: Physics at TeV colliders, Les Houches, 26 May - 6 June, 2003

*QCD event generators with next-to-leading order matrix-element and parton showers*, Y. Kurihara, Workshop: Physics at TeV colliders, Les Houches, 26 May - 6 June, 2003

*Looking for a simple method to combine "hard + 0 jet" and "hard + 1 jet" event generators*, S. Odaka, Workshop: Physics at TeV colliders, Les Houches, 26 May - 6 June, 2003

*Event Generator Development at KEK*, S. Odaka, Atlas Physics Workshop, Lund, 12 - 16 Sep., 2001*Integration of GRACE and PYTHIA*, S. Odaka, VII International Workshop on Advanced Computing and Analysis Techniques in Physics Research (ACAT2000), FNAL, 16 - 20 Oct., 2000**Here are some slides in Japanese.**

Members

Atlas-Japan

- Shigeru ODAKA (chair), KEK
- Soushi TSUNO , KEK

- Junpei FUJIMOTO , KEK
- Yoshimasa KURIHARA , KEK
- Tadashi ISHIKAWA , KEK
- Toshiaki
KANAKO , KEK

- Kiyoshi
KATO , Kogakuin U.