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Les Houches

2021 Session

Wikis of Previous sessions

Les Houches Themes



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SM: Loops, Multi-legs, Jets

List of Topics

1) PDFs

a) impact of LHC data, current and future

  • -how well do we know PDFs at high x→implications for new physics
  • -how Gaussian are high x PDF uncertainties, i.e. what would it take to believe a high mass excess

b) impact of/need for an LHeC

c) combination of PDF sets

d) impact of NNLO jet calculations


a) wishlist of calculations→ review of what current exists→input: what do the experiments really want?

b) study of the 'Sudakov Zone', ~1 TeV where EWK corrections may be comparable to QCD corrections

c) PDFs with QED corrections, photon PDFs, gamma-gamma processes

d) press ahead with the tuned comparison of precision calculations for Drell-Yan processes carried out in the framework of the LPCC EW Group

e) prescriptions for combining QCD and EW corrections


Binoth Les Houches Accord (BLHA)

a) An update on this is in the make.

The details are in the new version of the draft:

Pdf file of the updated write-up

Summary of the main points agreed on in the meeting of June 5:

Passing Parameters:

function: OLP_SetParameter(char*, &double,&double, int)

The keywords for the particle masses and widths are defined by their PDG codes, names for couplings are defined in the write-up, e.g. for the top mass, width, sin^2\theta_w: mass(6), width(6), sw2

Note that these parameters can be complex (two doubles as function arguments).

Global settings like MassiveParticles, (In)ActiveParticles

should also be possible.

Treatment of unstable phase space points:

no changes with respect to the last version of the draft

different powers of coupling constants:

allow different settings for different subprocesses

example: orderQCD 2 (global setting)

process x orderQCD 3 ; orderQED 1 (use these orders in alpha_s, alpha only for process x)

process y orderQCD 4 ; orderQED 0

This setup can be used for merged samples as well as mixed QCD/EW corrections. It can also be used to pass additional information referring only to particular subprocesses, e.g.

process x orderQCD 3 ; orderQED 1 ; AmplitudeType LoopInduced

EW corrections:

no changes wrt the last version of the draft. Importance to keep the EW Scheme option “UserDefined” was stressed.


Conventions for polarisation vectors already have been fixed at the last meeting. For special options concerning colour (terms in 1/N expansion, not colour summed, etc) it was felt that this should be “hardwired” between the particular OLP/MC providers to follow the individual needs.

Restrictions such as diagram filters, exploitation of special symmetries, etc:

Also rather something where the particular OLP/MC providers (humans) should talk to each other.

Test cases to try out implementation of the new settings:

Z+1/Z+2 jets; dijet/3jets

Test cases will be discussed on Monday June 10, 15h00, Library

b) Implementation of corrections (in particular EW) in Monte Carlo programs (e.g. Sherpa)

4) Top Decays a) handling top decays in processes like tTH, tTbB and tTjj

Coordination with Snowmass: QCD Issues

2013/groups/sm/start.1370465077.txt.gz · Last modified: 2013/06/05 22:44 by gudrun.heinrich