REVIEW
Higgs production at the lHC
High Energy Physics - Phenomenology · Submitted 2 Dec 2010 · 79 references
Pith's verdict: A solid, transparent uncertainty budget for Higgs production at 7 TeV; the headline percentages are prescription-dependent at the ten-point level, which the paper mostly admits.
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Referee report
The paper
The paper claims
The gluon-fusion Higgs rate at 7 TeV comes with a theory error of roughly a quarter, and the authors argue the error budget should be quoted rather than assumed away.
The reading
What carries the argument
The load-bearing device is a prescription for combining uncertainties that have no statistical meaning. The authors insist that scale variation, the effective-theory approximation, and the spread of parton parametrizations are all theoretical, with flat priors, so they cannot be added in quadrature the way an experimental collaboration would. They propose three procedures — apply the PDF-plus-$alpha_s$ band on top of the maximal and minimal scale-varied cross sections and add the scheme error linearly (procedure A); add everything linearly (B); or take the envelope over different next-to-next-to-leading-order parton sets (C) — and show that A and B agree to a few percent. Around this sits the calculational stack: the HIGLU code for exact next-to-leading-order gluon fusion with finite quark masses, the infinite-mass next-to-next-to-leading-order piece normalized to the exact leading order, and grids for the electroweak and mixed corrections. For the supersymmetric channels the same logic is applied to a next-to-leading-order gluon-fusion calculation with only the bottom loop retained and to the next-to-next-to-leading-order bottom-fusion code, with a wider scale window in the latter case to absorb the scheme ambiguity that cannot be varied directly.
Extended reading notes
Core claim
The paper's central claim is that the Standard Model Higgs production cross section in gluon fusion at $7$ TeV carries a total theoretical uncertainty of approximately $-25/+30$ percent for $M_H < 200$ GeV and about $20$ percent at higher masses, and that this uncertainty is dominated by three comparably sized, non-statistical sources that should be combined linearly rather than in quadrature. The individual pieces are: a scale variation of about $10$ percent obtained by varying $mu_R$ and $mu_F$ between $M_H/4$ and $M_H$ around a central scale $mu_0 = M_H/2$; a parton-distribution plus strong-coupling uncertainty of $11$ to $15$ percent, built from the MSTW Hessian eigenvectors, the experimental error on $alpha_s$, and an added theoretical error on $alpha_s$; and an effective-field-theory uncertainty of $3$ to $7$ percent from the infinite-top-mass approximation used beyond next-to-leading order, together with the scheme dependence of the bottom-quark mass. The authors stress that the resulting band is noticeably tighter than the roughly $-35/+40$ percent they previously found at the Tevatron, because the QCD K-factors are smaller at $7$ TeV and the relevant gluon momentum fractions are less extreme. For the supersymmetric case, adding the bottom-mass scheme ambiguity, the parametric bottom-mass error, and the bottom density in the proton pushes the total to about $50$ percent in both $gg to Phi$ and $b bar b to Phi$, which translates into a factor of about $sqrt{2}$ on the $tan beta$ values that can be excluded.
Load-bearing premise
The headline percentages depend on judgement calls rather than derived results: the central scale is set to half the Higgs mass and the variation window to a factor of two precisely because that choice makes the lower-order band bracket the higher-order central value, and the supersymmetric bottom-mass scheme error is assigned by hand at 15 percent.
Editorial extensions
If this is right
- Exclusion limits on the Standard Model Higgs mass derived from the $7$ TeV gluon-fusion channel should be quoted with a rate uncertainty near $25$ percent at low mass, not the smaller numbers used in early experimental combinations.
- Because the branching ratios to $WW$, $ZZ$, and $gamma gamma$ inherit $3$ to $10$ percent parametric uncertainties in the intermediate mass region where $b bar b$ and $WW$ compete, the uncertainty on cross section times branching ratio is larger than the cross section uncertainty alone in that window.
- The same uncertainty budget carries over almost unchanged to $8$, $9$, and $10$ TeV running, so cross sections measured at those energies inherit the $7$ TeV error band even though the central rates rise by $20$ to $100$ percent.
- In the supersymmetric case, a $50$ percent rate uncertainty means the $tan beta$ reach of the early run is weaker by about a factor of $sqrt{2}$ than a central-value estimate would suggest.
- Any future global fit that treats the gluon-fusion rate as a precision observable must inflate its error bar to match this budget or it will draw unjustified conclusions about Higgs couplings.
Reading between the lines
- The paper's insistence on linear combination is really a statement about how to report a prediction that has a flat-prior uncertainty: if the community adopted it uniformly, many quoted Higgs signal strengths would acquire visibly asymmetric error bars, which would in turn change how much room is left for new physics in coupling fits.
- The fact that the effective-theory error is estimated by rescaling an exact-versus-approximate difference with a ratio of K-factors suggests a concrete improvement path: a fully finite-mass next-to-next-to-leading-order calculation would replace an estimate with a number, and the size of the shift would test whether the estimate was conservative.
- The observation that the $7$ TeV uncertainty is smaller than the Tevatron one because the relevant gluon momentum fractions are less extreme implies that the error budget is a function of energy in a way that could be mapped and used to choose an optimal running energy for a precision Higgs measurement, a question the paper raises but does not pursue quantitatively.
- The authors note in passing that the decay $H to gg$ carries a residual scale dependence of about $10$ percent at next-to-next-to-leading order, which they discard because the branching ratio is small; if that channel ever becomes a discovery mode, that neglected error would need to be reinstated and could dominate the budget.
Original abstract
We analyze the production of Higgs particles at the early stage of the CERN large Hadron Collider with a 7 TeV center of mass energy (lHC). We first consider the case of the Standard Model Higgs boson that is mainly produced in the gluon-gluon fusion channel and to be detected in its decays into electroweak gauge bosons, $gg\to H \to WW,ZZ,\gamma\gamma$. The production cross sections at $\sqrt s=7$ TeV and the decay branching ratios, including all relevant higher order QCD and electroweak corrections, are evaluated. An emphasis is put on the various theoretical uncertainties that affect the production rates: the significant uncertainties from scale variation and from the parametrization of the parton distribution functions as well as the uncertainties which arise due to the use of an effective field theory in the calculation of the next-to-next-to-leading order corrections. The parametric uncertainties stemming from the values of the strong coupling constant and the heavy quark masses in the Higgs decay branching ratios, which turn out to be non-negligible, are also discussed. The implications for different center of mass energies of the proton collider, $\sqrt s=8$-10 TeV as well as for the design energy $\sqrt s= 14$ TeV, are briefly summarized. We then discuss the production of the neutral Higgs particles of the Minimal Supersymmetric extension of the Standard Model in the two main channels: gluon-gluon and bottom quark fusion leading to Higgs bosons which subsequently decay into tau lepton or $b$-quark pairs, $gg, b\bar b \to {\rm Higgs} \to \tau^+\tau^-,b\bar b$. The Higgs production cross sections at the $\lhc$ and the decay branching ratios are analyzed. The associated theoretical uncertainties are found to be rather large and will have a significant impact on the parameter space of the model that can be probed.
The compiled record
The paper's own sentences, arranged, kept beside the review and separate from it. Each label is drawn from a closed vocabulary; the number beside it is the probability the classifier gave that label. Numbers in the tables are the authors', checked by code. No sentence in this record was written by a model.
The abstract, sentence by sentence
We analyze the production of Higgs particles at the early stage of the CERN large Hadron Collider with a 7 TeV center of mass energy (lHC). We first consider the case of the Standard Model Higgs boson that is mainly produced in the gluon-gluon fusion channel and to be detected in its decays into electroweak gauge bosons, $gg\to H \to WW,ZZ,\gamma\gamma$. The production cross sections at $\sqrt s=7$ TeV and the decay branching ratios, including all relevant higher order QCD and electroweak corrections, are evaluated. An emphasis is put on the various theoretical uncertainties that affect the production rates: the significant uncertainties from scale variation and from the parametrization of the parton distribution functions as well as the uncertainties which arise due to the use of an effective field theory in the calculation of the next-to-next-to-leading order corrections. The parametric uncertainties stemming from the values of the strong coupling constant and the heavy quark masses in the Higgs decay branching ratios, which turn out to be non-negligible, are also discussed. The implications for different center of mass energies of the proton collider, $\sqrt s=8$-10 TeV as well as for the design energy $\sqrt s= 14$ TeV, are briefly summarized. We then discuss the production of the neutral Higgs particles of the Minimal Supersymmetric extension of the Standard Model in the two main channels: gluon-gluon and bottom quark fusion leading to Higgs bosons which subsequently decay into tau lepton or $b$-quark pairs, $gg, b\bar b \to {\rm Higgs} \to \tau^+\tau^-,b\bar b$. The Higgs production cross sections at the $\lhc$ and the decay branching ratios are analyzed. The associated theoretical uncertainties are found to be rather large and will have a significant impact on the parameter space of the model that can be probed.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | We analyze the production of Higgs particles at the early stage of the CERN large Hadron Collider with a 7 TeV center of mass energy (lHC). | contribution 0.94 | 0.85 | 0.03 | asserted 0.94 |
| s1 | We first consider the case of the Standard Model Higgs boson that is mainly produced in the gluon-gluon fusion channel and to be detected in its decays into electroweak gauge bosons, $gg\to H \to WW,ZZ,\gamma\gamma$. | contribution 0.81 | 0.20 | 0.04 | asserted 0.99 |
| s2 | The production cross sections at $\sqrt s=7$ TeV and the decay branching ratios, including all relevant higher order QCD and electroweak corrections, are evaluated. | method 0.46 | 0.92 | 0.05 | asserted 1.00 |
| s3 | An emphasis is put on the various theoretical uncertainties that affect the production rates: the significant uncertainties from scale variation and from the parametrization of the parton distribution functions as well as the uncertainties which arise due to the use of an effective field theory in the calculation of the next-to-next-to-leading order corrections. | contribution 0.40 | 0.71 | 0.09 | asserted 0.99 |
| s4 | The parametric uncertainties stemming from the values of the strong coupling constant and the heavy quark masses in the Higgs decay branching ratios, which turn out to be non-negligible, are also discussed. | result 0.65 | 0.84 | 0.05 | asserted 1.00 |
| s5 | The implications for different center of mass energies of the proton collider, $\sqrt s=8$-10 TeV as well as for the design energy $\sqrt s= 14$ TeV, are briefly summarized. | interpretation 0.42 | 0.74 | 0.04 | asserted 0.78 |
| s6 | We then discuss the production of the neutral Higgs particles of the Minimal Supersymmetric extension of the Standard Model in the two main channels: gluon-gluon and bottom quark fusion leading to Higgs bosons which subsequently decay into tau lepton or $b$-quark pairs, $gg, b\bar b \to {\rm Higgs} \to \tau^+\tau^-,b\bar b$. | contribution 0.98 | 0.77 | 0.04 | asserted 0.95 |
| s7 | The Higgs production cross sections at the $\lhc$ and the decay branching ratios are analyzed. | contribution 0.92 | 0.87 | 0.05 | asserted 0.94 |
| s8 | The associated theoretical uncertainties are found to be rather large and will have a significant impact on the parameter space of the model that can be probed. | interpretation 0.66 | 0.91 | 0.26 | asserted 0.97 |
What was examined, and what was not
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Figures
Showing 20 of the paper's 21 figures. See all figures in the PDF ↗ Figures reproduced from arXiv:1012.0530 by the authors.
References
How later papers used it
67 later papers cite it
5 later papers by other authors are listed below: 5 used its data or values. 2 more papers by the same authors are listed: 1 used its method or tool and 1 used its data or values.
Uses its method or tool 1 of 3 papers with this label · 1 by the same authors
By the same authors
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Used the procedure of this paper to find a total uncertainty of +16%/-19% in the ttbar production cross section.
Implications of the ATLAS and CMS searches in the channel $pp \to Higgs \to \tau^+\tau^$ for the MSSM and SM Higgs bosons (2011) (same authors) · 0.80 · paraphrased: the licence does not allow quoting
Uses its data or values 6 of 25 papers with this label · 1 by the same authors
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Used the K-factor from this paper, about 2.5 at 7 and 8 TeV and about 2 at 14 TeV, to calculate the NNLO cross section from the LO one.
Extending the Higgs sector: an extra singlet (2015) · 0.93 · paraphrased: the licence does not allow quoting
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Took from this paper the 14 TeV LHC cross section for gg to h' at 1000 GeV and multiplied it by 0.9 to get the 13 TeV values.
Gauge Singlet Vector-like Fermion Dark Matter, LHC Diphoton Rate and Direct Detection (2017) · 1.00 · paraphrased: the licence does not allow quoting
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Used the uncertainties on the branching fraction for H to W+W- from this paper.
Combined CDF and D0 Upper Limits on Standard Model Higgs Boson Production with up to 8.2 fb-1 of Data (2011) · 1.00 · paraphrased: the licence does not allow quoting
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Used the uncertainties on the branching fraction for H to W+W- from this paper.
Updated Combination of Searches for the Standard Model Higgs Boson at the D0 Experiment in 9.7 fb-1 of Data (2012) · 1.00 · paraphrased: the licence does not allow quoting
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Multiplied the production cross section by a K-factor of 1.3 from NNLO results of this paper.
Measuring the Invisible Higgs Width at the 7 and 8 TeV LHC (2011) · 0.95 · paraphrased: the licence does not allow quoting
By the same authors
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Took the inclusive cross sections for ggF, VBF and VH from this paper, assuming SM proportions.
Direct detection of Higgs-portal dark matter at the LHC (2012) (same authors) · 1.00 · paraphrased: the licence does not allow quoting
How the literature uses it
67 arXiv papers cite this in 105 sentences
Papers citing it · 57 sentences without a confident label
Contests it 1 paper
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[ref] . * The claim [ref] that the HERAPDF1.0 NNLO set with $α_S(M_Z^2)=0.1145$ lowers the Higgs cross section compared to MSTW08 by $≈40%$ for $M_H≈160$ GeV at the Tevatron is due to a mistake in the calculation, and therefore the conclusions in the published version of ref.
PDF dependence of Higgs cross sections at the Tevatron and LHC: response to recent criticism · Conclusions · contest 0.92
Uses its method or tool 3 papers
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Using those formulae we were able to express the production factors in terms of next-to-leading order cross sections for each of the mechanisms considered, calculated using HIGLU [ref] for the gluon-gluon cross section, bb@nnlo [ref] for the $b b̅$ process and reference [ref] (and references therein), for the remaining processes, all multiplied by the adequate factors pertaining to the mixing of scalar-pseudoscalar states.
Probing the scalar-pseudoscalar mixing in the 125 GeV Higgs particle with current data · A specific model for scalar-pseudoscalar mixing · 0.96
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We have evaluated them with HATHOR [ref] and, in the production channel $σ(p p → tt̅)$ and for $m_t= 173.3 ± 1.1$GeV, we find $σ(p p →tt̅)= 163 ^+2.5%_-5.6% (factor 2 from central m_t scale) ^+10.4%_-10.1% (PDF+Δ^exp+thα_s@90%CL) ±3.3% ( Δm_t)$ pb, which leads using the procedure of Ref. [ref] to a total uncertainty of $Δσ/σ= ^+16%_-19%$, i.e three times larger than the one assumed in the CMS analysis.
Implications of the ATLAS and CMS searches in the channel $pp \to Higgs \to \tau^+\tau^$ for the MSSM and SM Higgs bosons · 4. Implications in the MSSM for higher luminosities · 0.80
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We generate our signal events $h$+jets using MadGraph's native MLM matching [ref] scheme and normalize to the inclusive production cross section of $h$+jets at NNLO from Ref. [ref] to account for the large $K$-factor from next-to-leading order (NLO) and next-to-next-to-leading order (NNLO) corrections.
Measuring the Invisible Higgs Width at the 7 and 8 TeV LHC · Monojet Searches · 0.90
Uses its data or values 25 papers
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The uncertainties induced by the use of the EFT approach at NNLO are estimated, from the NLO case in which both the exact and EFT calculations are available, to be of $O(9%)$ for $M_H≈126$ GeV [ref] .
The apparent excess in the Higgs to di-photon rate at the LHC: New Physics or QCD uncertainties? · Introduction · 0.85
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We display the predicted event yields $N_inv^gg$, $N_inv^V$ in, respectively, the ggF and VBF+VH channels for the four CMS $p_T^miss$ cuts.[ Note that we did not consider the theoretical uncertainties on the cross sections [ref] and the efficiencies of the $p_T$ cuts which, although significant, are currently smaller than the experimental ones.] For convenience, we also reproduce the expected $ΔN_95 %^i,exp$ and observed $ΔN_95 %^obs$ 95% CL limits on the number of extra non-SM events quoted by CMS in Ref. [ref] for each cut.
Direct detection of Higgs-portal dark matter at the LHC · Monojet constraints on the invisible width · 0.82
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$σ(gg→ϕ)$ is obtained using Eq. ([ref]) and the $σ(gg→h)$ from Ref. [ref] as mentioned earlier.
Extra Neutral Scalars with Vector-like Fermions at the LHC · Model-independent Analysis · 0.96
Compares with it 1 paper
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Our results published in Ref. [ref] agree with those given in Refs. [ref] and updated in Ref. [ref] within a few percent.
Phenomenology of the Higgs at the hadron colliders: from the Standard Model to Supersymmetry · The main channel at the lHC (or LHC at 7 TeV) · 1.00
Cites it as background 12 papers
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For calculations of Higgs production cross sections in the SM see for example [ref] and [ref] in fourth generation models.
Higgs Search Constraints on Fourth Generation Scenarios with General Lepton Sectors · Higgs production and decay · 0.80
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Below, I summarise the main features and refer the reader to [ref] and references therein for further details.
Higgs Physics at the Large Hadron Collider · Production of the Higgs at the LHC · 0.90
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The accuracy of the $M_t→∞$ approximation at NNLO has been investigated in Refs. [ref] .[Scale, PDF, strong coupling and heavy-top-limit uncertainties have recently been reappraised in Ref. [ref] .]
Inadequacy of zero-width approximation for a light Higgs boson signal · Introduction · 0.92
What it cites · 12 sentences without a confident label
Uses data or values from 3 papers
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Analyses performed by the CDF and D0 experiments, under some assumptions for the production cross sections and their associated uncertainties, have recently excluded the Higgs mass range $M_H=158$–175 GeV at the 95% confidence level (CL) [ref] .
Combined CDF and D0 Upper Limits on Standard Model Higgs-Boson Production with up to 6.7 fb-1 of Data · Introduction · 0.89
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In the later case, two sets are provided: one with the value $α_s=0.1176$ that is close to the world average value [ref] and the MSTW best–fit $α_s=0.1171$ [ref] , and one with the value $α_s=0.1145$ used also in the ABKM set [ref] , that is close to the preferred values that one obtains using deep–inelastic scattering data alone.
The 3-, 4-, and 5-flavor NNLO Parton from Deep-Inelastic-Scattering Data and at Hadron Colliders · The PDFs and $α_s$ uncertainties · 0.90
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The MSTW collaboration has recently released a set of PDFs with different bottom quark masses [ref] : it involves six different central PDFs with a range of on–shell $m_b$ values between $4.00$ GeV and $5.50$ GeV in $0.25$ GeV steps, in addition to the central best–fit with $m_b=4.75$ GeV.
Heavy-quark mass dependence in global PDF analyses and 3- and 4-flavour parton distributions · The theoretical uncertainties · 0.85
Compares with 1 paper
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This overall uncertainty is much larger than the uncertainty assumed in the CDF and D0 combined analysis that excluded the SM Higgs boson at the 95% CL in the mass range $M_H=158$–175 GeV [ref] .
Combined CDF and D0 Upper Limits on Standard Model Higgs-Boson Production with up to 6.7 fb-1 of Data · Introduction · 0.96
Discussion
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