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LHC Higgs Cross Section Working Group LoI
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After two years of activities the HXSWG is undergoing substantial
restructuring while keeping the original motivations.
Consequently, our primary goal will remain the same: give EXPs
a clear guideline for Higgs analysis, including associated uncertainties.

Our plan is to make the HXSWG more effective in supporting the LHC
needs, i.e. we propose the new groups

1) light Higgs / property measurements
2) BSM Higgs

A lot of discussions are taking place inside ATLAS and CMS on Higgs
Combination and Properties.
It is the right moment to reinforce the message that the HXSWG is the natural
place to keep alive a discussion on theoretical issues, providing tools,
theory uncertainties, strategies for property measurement etc.

The new structure:

The main groups comprise:

 0. The production groups:
    * ggF [H -> gaga, WW, ZZ]
      Contacts: ATLAS: 	Biagio di Micco
                	CMS  :
                	TH   : 	Daniel de Florian, Kirill Melnikov, Frank Petriello
    * VBF [H -> gaga, tautau, WW, ZZ]
      Contacts:	ATLAS: 	Daniela Rebuzzi
                	CMS  :
                	TH   : 	Ansgar Denner(tbc), Carlo Oleari
    * WH/ZH [H -> bb]
      Contacts:	ATLAS: 	Giacinto Piacquadio
                	CMS  : 	Jim Olsen
                	TH   : 	Stefan Dittmaier, Giancarlo Ferrera
    * ttH [H -> bb]
      Contacts:	ATLAS: 	
                	CMS  : 	Jim Olsen
                	TH   : 	Laura Reina, Michael Spira

    These groups should continue with
    - the calculation of 8 TeV predictions (and possibly prepare other
      energies)
    - provide easy-to-use tools for distributions
    - include further updates in the predictions
    - and should cover specific issues related to Higgs decay in
      each production process (with the most relevant decay channels
      indicated above [...])

 1. Light Mass (LM) Higgs
    i)  issues concerning XS * BR, in particular issues connected
        to the decays H -> gamma+gamma, tau+tau, bb, WW and ZZ
    ii) Higgs property measurements: Higgs mass, (width), sigma*BR, J^PC,
                                     couplings (HVV, Yukawa, trilinear, quartic).

    Discuss main theoretical issues (concerning XS * BR)
    and create tools to be used by ATLAS and CMS (+CDF+D0) to
    analyze Higgs boson data available in 2012 and beyond, including
    branching fractions, couplings to SM particles, anomalies in the present
    data (gamma+gamma and WW signals), evidence of spin zero and how
    this possibility could be confirmed in the near future,
    separation of signal and backgrounds and strategy for measuring
    the mass and other characteristics of a putative signal.

      Contacts:	ATLAS: 	Michael Duehrssen, Markus Schumacher
                	CMS  : 	Andre David, Markus Klute
                	TH   : 	Massimiliano Grazzini, Ansgar Denner(tbc),
                       		Georg Weiglein

 2. MSSM            Neutral - Charged Higgs merged
    Cross sections have to worked out in more detail, more channels,
    higher precision, similar for distributions.

      Contacts:	ATLAS: 	Trevor Vickey, Martin Flechl
                	CMS  : 	Monica Vasquez, Sami Lethi
                	TH   : 	Robert Harlander, Michael Kraemer,
                       		Pietro Slavich, Michael Spira

 3. BSM      	BMSSM, ..., XMSSM, heavy Higgs bosons

      Contacts: ATLAS: 	Krisztian Peters, Sara Diglio
                	CMS  : 	Mario Kadastik, Sara Bolognesi
                	TH   : 	Christophe Groan

    Branching fractions, couplings, e.g. to an hypothetical invisible sector
    to determine their current favourite values.

    Concerning a possible BSM heavy Higgs boson:
    i)  H-> WW,ZZ, Interference,
    ii) VV-scattering

    While the signal modeling of a light Higgs is very well studied,
    additional work is needed in the case when the Higgs is heavy and
    has a large width. We should plan in particular to discuss
    the treatment of the Higgs width, and of the signal-background
    interference effects in parton shower Monte Carlos, fixed order
    calculations, and their combination.


 4. BR (SM, MSSM)
    SM BRs to be refined if required (by new calculations...)
    MSSM BRs to be worked out for general applications
    Distributions?

      Contacts:	ATLAS: 	Daniela Rebuzzi
                	CMS  : 	Ivica Puljak
                	TH   : 	Alexander Mueck, Sven Heinemeyer

 5. PDF subgroup will act as contact for PDF4LHC and as a support group.

      Contacts: TH   : 	Joey Huston, Stefano Forte, Robert Thorne

 6. NLO MC experts will be kept to give the needed support when required
    by each subgroup.

      Contacts: TH   : 	Stefano Frixione(tbc), Frank Krauss(tbc),
                       		Fabio Maltoni(tbc), Paolo Nason(tbc)


The previous PO group is integrated (by definition!) in LM and the HM part
of BSM.

While keeping the existing Higgs production and decay subgroups, we
think that LM comprises the most important new issues for next two
years (even though we should pursue also a heavy Higgs (within BSM),
especially in case of total exclusion of light Higgs with 2012 data.)

Where necessary, links with corresponding ATLAS/CMS working groups
should be established.
Similarly, any theoretical issues should be collected by the contacts.
Feedbacks to the collaborations of any agreed recommendations should
be made immediately.


April 10, 2012
Sven Heinemeyer, Chiara Mariotti, Giampiero Passarino, Reisaburo Tanaka