Jets subgroup

Goal of the group

Group Contacts

Daniele del Re (CMS)

Bruce Mellado (ATLAS)

Gavin Salam (Theory)

Frank Tackmann (Theory)

Available Tools

Settings for comparison studies

H+2-jet NLO+shower comparison study

Process/Inputs:
===============

* pure gg -> H + 2j NLO+shower at parton level

* m_H = 125 GeV
* \sqrt{s} = 8 TeV
* strict mtop -> \infty limit (no mtop rescaling or bottom interference)
* on-shell stable Higgs
* MSTW2008 NLO PDFs (68CL) (always also at LO)
  with its alphas(mZ) = 0.12018, nf = 5, 2-loop running
* \mu_r = \mu_f = \mu = m_H in (N)LO hard matrix element corrections


Jet cuts:
=========

(\eta is pseudorapidity, y is rapidity)

a) Jet selection:
* anti-kT with R = 0.4
* at least two jets with pTj > 25 GeV and |\eta_j| < 5

b) VBF cuts:
* \delta y_jj = |y_j1 - y_j2| > 2.8
* m_jj > 400 GeV


Distributions:
==============

All distributions with
* only cuts a) and cuts a)+b)
* at LO and NLO each with \mu = {2 m_H, m_H, m_H/2}

1) pTj1 [0, 300] in steps of 5 GeV
2) pTj2  [0, 300] in steps of 5 GeV
3) yj1 [-5, 5] in steps of 0.5
4) yj2 [-5, 5] in steps of 0.5
5) |\delta\y_jj| [0,10] in steps of 0.5
6) m_jj [0, 1000] in steps of 40 GeV

7) \Delta\phi_jj [0, Pi] in steps of Pi/20
8) pTj3 [0, 300] in steps of 5 GeV
9) yj3 [-5, 5] in steps of 0.5

10) |eta_H - 0.5(\eta_j1 + \eta_j2)| [0,10] in steps of 0.5
11) pT_{Hjj} = |\vec{p}_{TH} + \vec{p}_{Tj1} + \vec{p}_{Tj2}| [0, 300] in steps of 5 GeV
12) Pi - \Delta\phi_{H,jj} [0, 1.5] in steps of 0.05

Results

First comparisons can be found here.

Guidelines for UE related uncertainties

The following are guidelines for the estimation of UE related uncertainties in ggF and VBF processes:

1) Turn UE on/off for the nominal default tune (expect ~10-20% variations depending on selection cuts and tune)

2) Cross check on/off effect for alternative tunes (that are also deemed "reasonable")

3) Cross checks can include the use of tunes performed within a common framework but using different PDFs (eg. NLO v. LO, as is the case with AU2-CT10 and AU2-CTEQ6L1)

First studies can be found here and these studies will continue past the Moriond conferences. Until these guidelines can be implemented, the following temporary uncertainties are suggested:

1) For ggF+2j use 30% uncertainty

2) For VBF use 7% uncertainty

These uncertainties pertain to the normalization of both samples in the loose and tight VBF categories.

References

Meetings

• 18/05/12
• 12/10/12
• 29/11/12
• 20/12/12
• 08/02/13
• 25/01/13

Links

-- ReiTanaka - 02-May-2012