data vs theory Joey Huston Bruce Mellado 1 Higgsgt gg jets Most of the excess observed for Higgs production is in gt1 jet final states Maybe CMS does not see as large of an excess ID: 324385
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Slide1
Higgs+jets: data vs theory
Joey HustonBruce Mellado
1Slide2
Higgs(->gg)+jets
Most of the excess observed for Higgs production is in >=1 jet final statesMaybe CMS does not see as large of an excess
In any case, we would like to use the best theory we can to understand the level of excess
For inclusive Higgs production through
gg fusion, we use a NNLO+NNLL calculationwhich means a NLO calculation for Higgs + 1 jetand a LO calculation for Higgs + 2 jets
2Slide3
NNNLO inclusive
gg->Higgs cross section is not very convergentSo it’s appropriate to think about effects of still higher order corrections
Approximate NNNLO corrections have been carried out
resumming
the effects of soft gluon radiation; recently BFKL logs have been resummed as well, leading to more scale stability and an additional increase in the cross section
This increase should be
p
assed on to the 1 and 2
j
et cross sections as well
3Slide4
Higgs+1 jet at NLO
…from Dec. 20 meetingNLO cross section has a LO-like scale dependence
4Slide5
Higgs+1 jet at NNLO
So the NNLO correction for Higgs+1 jet (through gg fusion) is about 30%gg
corresponds to about 65% of the cross section; they are working on other initial states and it is probable that the NNLO corrections for the other initial states (
gq
) will be somewhat smaller (maybe 1.15 instead of 1.30)
σ
NLO
/
σ
LO
= 1.6
σ
NNLO
/
σ
NLO
= 1.3
arXiv:1302.6216
5Slide6
Higgs+jets (binned cross sections)
r
esummation
for Higgs + 0 jet
and for Higgs + 1 jet has lead
to sizeable reduction in scaleuncertainty for exclusive Higgs
+0,1 jet production
w
e need to revisit the formulation of the
u
ncertainties for binned jet Higgs cross
s
ections
t
his is a task for Snowmass/
Les
Houches
a
lso investigate jet veto effects for higher
e
nergy accelerators
Xiaohui
LiuSlide7
What about Higgs+>=2 jet final states?
We know Higgs+2 jets to NLOA NNLO calculation of Higgs+2 jets is a long way off, but by general arguments we might expect the size of the NNLO corrections to be <= that seen for Higgs+1 jet
7Slide8
Sherpa+…
One of the best vehicles to estimate contributions to the different jet multiplicities may be Sherpa(+gosam/MCFM/
blackhat
)
At least it’s the one I’m currently usingOne can include Higgs+0,1 and 2 jets at NLO, up to 3 additional jets at LO, with extra jets from parton showers, looking at the effects of varying the merging scale, the renormalization scale, the factorization scale and the resummation scale
with maybe some motivated re-weighting based on the new theory predictionsI have Higgs+1 jet (at NLO) working now, and should have Higgs+2 jets in the next few days
The same thing can be done for
W+jets
, so this may be a useful cross-check in a channel where the statistics are much higher and the physics perhaps better understood
We know we see an excess
It may be a fluctuation, we would like to understand the theory predictions and their uncertainties.
2
nd
jet
r
eceives
s
ubstantial
c
ontributions
f
rom 3-jet
m
atrix
element
8