Description

Accurate predictions for the differential signal cross sections in the SM in gluon-gluon fusion (NNLO in the EFT, top-quark mass effects at NLO, NLO+PS, merged and matched samples), especially as a function of the Higgs trilinear coupling.

*HH subgroup meeting, 20th October 2014*

----------------------------------------------------------------------------------------

Q == Question

A == Answer

C == Comment

Action

**Introduction: Roberto Salerno**

List of topics the HH subgroup plans to cover and approximate deadlines

Q: What about VBF HH?

A: Part of our charge is to deploy a program to compute differential cross sections in VBF.

**1. speaker: Michel Spira
"Theoretical Aspects of Higgs Pair Production @ LHC”**

Q (Sally Dawson): How to choose scales? Dynamic vs Fixed scale?

A (Michael Spira): It needs to be discussed in detail. The dynamic (Q^2-dependent) scale should be chosen, depending on the subject of study. In the case of di-Higgs production m_HH, in case of HH+jets something like m_HH+pT.

Q: How about bbWW being hopeless? Isn’t it premature, why dismiss it now?

A (Michael Spira): It was “provocative” in the talk. We need an analysis from the experimental side

C: fully leptonic channels (completely hopeless) and semi leptonic (could be promising).

C: Remember that investigation of semi-leptonics has been doing using MVA (not done in other channels).

C: 6ab-1 is extremely conservative, one can explore other final states (example VBF) and boost the discovery

C (Leandro Nisati): The positive interference is a strong reason to put qq->ttHH in the list of interesting channels.

Action: the discussion of the the possible final state signatures at the LHC will be the main topic of one of the next HH subgroup meeting.

**2. speaker: Eleni Vryonidou
"HH production : NLO+PS and top-quark mass effects in gg fusion”**

Q: How to estimate the uncertainty between the two approaches at NLO, yours and Spira’s (HPAIR)?

A: It should be about 10%

Q: Why full NLO correction are only 2%?

A: it’s not 2% on the exact result (we don’t have it) but there is a large cancellation between triangle and box.

Q: What about the error associated with the usage of Effective Field Theory?

A: It is not quoted here but it is of the order of 10% and that is what we see from different calculations from different groups.

Q (Michael Spira): In your scheme threshold cancellations are not exact

A: True, but this is not where the bulk of the x-section sits

Then Michael made a suggestion that corrections to the box and triangle are different and 10% uncertainty of the MG5 framework can be inferred from MSSM case with additional heavy scalar. (not sure if I got this one right).

**3. Jonathan Grigo
"Top quark mass effects (NLO) and matching coefficient (NNLO) for Higgs boson pair production"**

C: We have for the corrections from top mass effect +10% / -10% from 2 different groups,

this is an indication of the uncertainties is +/- 10%.

We need to compare the 2 calculations and understand where the different signs come from.

Suggestions:

*) apply the procedure for single Higgs production of 500 - 600 GeV (~ to the triangle in the HH) and see if it works

*) check for the real correction only.

Action: to be discussed. Personal note: it will be great if the two groups will arrive with the suggested checks at the next HH subgroup meeting in mid-November.

**4. Javier Mazzitelli **

**“Higgs Boson Pair Production at NNLO in the EFT”**

Q: soft-virtual approximation works better? Is it true? We need to be careful with the statement is not better.

A: The quality of the approximation should decrease with the collider energy

A: soft-virtual approximation works better for HH than for H;

A: disagree because mass effects are larger in HH

A: (Daniel de Florian): in Mellin space this is not true

Q: 90% C.L. MSTW08 sets —> other results use 68%

A: Only 1 pdf is used here at the end we will following the recommendation of the LHCPDF group

Q: Uncertainty coming from the use of the EFT is not included. Can you guess it?

A: It could be about 10% as in the NLO case.

**5. Andreas Papaefstathiou
"Higgs boson pair production: The road ahead" **

**Discussion: Magdalena Slawinska
Action: Check the central scale with different code**

C (Daniel de Florian): it can absorb part of the resummation if we change the scale (like in the single Higgs case). First we need the resummation.

----------------------------------------------------------------------------------------

There are minutes attached to this event.
Show them.