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Summing Large-$N$ Towers in Colour Flow Evolution

DESY-13-237
MCNET-13-21
arXiv:1312.2448
Eur.Phys.J. C74 (2014) 2907

by: Plätzer, Simon (DESY)

Abstract:
We consider soft-gluon evolution in the colour flow basis. We give explicit expressions for the colour structure of the (one-loop) soft anomalous dimension matrix for an arbitrary number of partons, and we show how the successive exponentiation of classes of large- $N$ contributions can be achieved to provide a systematic expansion of the evolution in terms of colour-suppressed contributions.

Colour reconnection and its effects on precise measurements at the LHC

LU-TP-13-37
MCNET-13-16
arXiv:1310.8073

by: Sjöstrand, Torbjörn (Lund U.)

Abstract:
There are experimental evidence for the occurrence of colour reconnection, but the mechanisms involved are far from understood. Previous reconnection studies are briefly summarized, and some potential implications for LHC physics are outlined.

Extracting $\sigma_{\rm effective}$ from the LHCb double-charm measurement

MAN-HEP-2013-20
MCNET-13-11
arXiv:1308.6749

by: Seymour, Michael H. (Manchester U.) et al.

Abstract:
We discuss various issues related to the definition of single and double open charm cross sections. We conclude that LHCb's extraction of sigma_effective, the effective cross section for double-parton scattering, is too large by a factor of two. This correction brings the data from open-charm pairs closer to that from J/psi plus open charm and jet production.

Update of the Binoth Les Houches Accord for a standard interface between Monte Carlo tools and one-loop programs

MPP-2013-237
arXiv:1308.3462
Comput.Phys.Commun. 185 (2014) 560-571

by: Alioli, S. (LBL, Berkeley) et al.

Abstract:
We present an update of the Binoth Les Houches Accord (BLHA) to standardise the interface between Monte Carlo programs and codes providing one-loop matrix elements.

Multiple Partonic Interactions in Herwig++

KA-TP-05-2013
MAN-HEP-2013-03
MCNET-13-02
arXiv:1302.4892
Acta Phys.Polon.Supp. 6 (2013) 613-620

by: Gieseke, Stefan (KIT, Karlsruhe, TP) et al.

Abstract:
We review the implementation of a model for multiple partonic interactions in Herwig++. Moreover, we show how recent studies on the colour structure of events in Herwig++ led to a significant improvement in the description of soft inclusive observables in pp interactions at the LHC.

ColorMath - A package for color summed calculations in SU(Nc)

LU-TP-12-40
MCNET-13-04
arXiv:1211.2099
Eur.Phys.J. C73 (2013) 2310

by: Sjödahl, Malin (Lund U.)

Abstract:
A Mathematica package for color summed calculations in QCD (SU(N ( )c( ))) is presented. Color contractions of any color amplitude appearing in QCD may be performed, and the package uses a syntax which is very similar to how color structure is written on paper. It also supports the definition of color vectors and bases, and special functions such as scalar products are defined for such color tensors.