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$tW$ and $tZ'$ production at hadron colliders
by Nikolaos Kidonakis, Marco Guzzi, Nodoka Yamanaka
This is not the current version.
|As Contributors:||Nikolaos Kidonakis|
|Arxiv Link:||https://arxiv.org/abs/2106.12910v1 (pdf)|
|Date submitted:||2021-06-25 08:08|
|Submitted by:||Kidonakis, Nikolaos|
|Submitted to:||SciPost Physics Proceedings|
We present theoretical results with soft-gluon corrections for two separate processes: (1) the production of a single top quark in association with a $W$ boson in the Standard Model; and (2) the production of a single top quark in association with a heavy $Z'$ boson in new physics models with or without anomalous couplings. We show that the higher-order corrections from soft-gluon emission are dominant for a wide range of collider energies. Results are shown for the total cross sections and top-quark transverse-momentum and rapidity distributions for $tW$ and $tZ'$ production at LHC and future collider energies up to 100 TeV. The uncertainties from scale dependence and parton distribution functions are also analyzed.
Submission & Refereeing History
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Reports on this Submission
Anonymous Report 3 on 2021-8-4 (Invited Report)
Two referee reports have already been provided for this proceeding, and I agree with their main point:
the overlap with ttbar production in the NLO QCD corrections has been completely ignored and as said in the report 1 “this applies also to the work this proceeding is based upon”.
The authors would be correct when they state that “The topic of tW and ttbar overlap is not directly relevant to our work which focuses on soft-gluon corrections in tW and tZ' production” if the proceeding was providing only formal results concerning the specific resummation contributions. On the other hand, predictions are then denoted as “approximated NLO (aNLO)” or even aNNLO or aNNNLO and then used for phenomenological conclusions. This is very misleading in my opinion without even mentioning in the discussion how the subtraction of the ttbar contribution is performed.
Furthermore there are statements like:
- “We show that the higher-order corrections from soft-gluon emission are dominant for a wide range of collider energies”. I do not see how this has been shown here, especially it is not clear to which class of contributions "dominant" refers to.
- “Perturbative QCD corrections are typically dominated by soft-gluon contributions”. In my opinion this is a too much strong statement. One can for example think about the very well known “Giant NLO QCD K-factors” in VV or V+jets processes, which are real hard QCD radiation effects.
- “soft-gluon corrections [1–4] are numerically dominant even at very high collider energies that are quite far from threshold  “ Is in reference  the ttbar overlap discussed? If not, where can be found the information about the removal/subtraction of the ttbar overlap at 100 TeV? This information should be properly referred in the proceeding.
-“We have demonstrated in all cases that higher-order corrections are large and are dominated by soft-gluon contributions” In the conclusion, this is a very strong statement not properly supported by results, since again the ttbar overlap has not been considered.
My general opinion is that a calculation of an important contribution to the tW and tZ’ cross section has been presented in a way that can be misleading and does not properly take into account or even mention a crucial technical and phenomenological issue in NLO or higher-order terms for this process. NLO predictions are on the other hand mentioned all over the text and used to build aNNLO and aNNNLO ones. Although this is a proceeding, nevertheless I think that this aspect cannot be neglected and what NLO means in this respect should be specified.
Anonymous Report 2 on 2021-7-27 (Invited Report)
This article does not contain new information directly, but rather summarises some relatively recent results obtained by the authors regarding soft-gluon corrections tW and tZ' production at hadron colliders. The authors correctly reference to these published results and for a proceedings it is quite normal to simply summarise the current situation.
The only improvement to this manuscript that I consider to be necessary is to also include the references to the NLO predictions presented in the plots (and not just to the articles where these plots were taken from), including the information on how the top pair production contributions were removed from these NLO calculations --I could not find the latter in the references from which the plots are taken. This would be needed to completely understand what is meant by "NLO".
Anonymous Report 1 on 2021-7-19 (Invited Report)
The authors present theoretical predictions for top and V (W, Z) associated production, including the effects of soft gluon resummation. Results are not original, as they are mostly based on previous work of the authors. However, this is quite usual for a conference proceeding, so I do not consider it as a weakness.
The main weakness I see is that (in general, this applies also to the work this proceeding is based upon) authors seem not to consider the quite vast literature about the problem of process overlapping between tW and ttbar at NLO (0805.3067, 0908.0631,1009.2450, 1607.05862). Such an overlapping, and the corresponding subtraction, introduce uncertainties which are of the order of ± 10%, roughly of the same size of the approximate-NNLO corrections.
As a matter of wording: The authors claim these effects to be'Large corrections': however, beyond NLO, effects are quite mild (10% or less as mentioned before). I would recommend a rephrasing.
After these points have been fixed, I can reconsider this work for publication on SciPost Proceedings.