اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدTowards precise predictions for Higgs-boson production in the MSSM
146
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
We study the production of scalar and pseudoscalar Higgs bosons via gluon fusion and bottom-quark annihilation in the MSSM. Relying on the NNLO-QCD calculation implemented in the public code SusHi, we provide precise predictions for the Higgs-production cross section in six benchmark scenarios compatible with the LHC searches. We also provide a detailed discussion of the sources of theoretical uncertainty in our calculation. We examine the dependence of the cross section on the renormalization and factorization scales, on the precise definition of the Higgs-bottom coupling and on the choice of PDFs, as well as the uncertainties associated to our incomplete knowledge of the SUSY contributions through NNLO. In particular, a potentially large uncertainty originates from uncomputed higher-order QCD corrections to the bottom-quark contributions to gluon fusion.
قيم البحث
اقرأ أيضاً
We analyse the production of a Higgs boson in association with a top--antitop-quark pair in the Standard Model at the LHC. Considering the final state consisting of four b jets, two jets, one identified charged lepton and missing energy, we examine t
he irreducible background for the production rate and several kinematical distributions. While ttH production and decay is roughly a fourth of the full process for the final state specified above, ttbb production constitutes the main contribution with about $92%$. Surprisingly, interference effects result in a reduction of the cross-section by five per cent. Furthermore, we consider NLO QCD corrections for the production of a Higgs boson, two charged leptons, two neutrinos, and two b jets. We discuss the size of the corrections and the scale dependence for the integrated cross section and different distributions. For the integrated cross section we find a $K$ factor of 1.17 and a reduction of the scale dependence from $30%$ at leading order to $5%$ at next-to-leading order.
Inclusive Higgs boson production at large transverse momentum is induced by different production channels. We focus on the leading production through gluon fusion, and perform a consistent combination of the state of the art calculations obtained in
the infinite-top-mass effective theory at next-to-next-to-leading order (NNLO) and in the full Standard Model (SM) at next-to-leading order (NLO). We thus present approximate QCD predictions for this process at NNLO, and a study of the corresponding perturbative uncertainties. This calculation is then compared with those obtained with commonly used event generators, and we observe that the description of the considered kinematic regime provided by these tools is in good agreement with state of the art calculations. Finally, we present accurate predictions for other production channels such as vector boson fusion, and associated production with a gauge boson, and with a $tbar{t}$ pair. We find that, at large transverse momentum, the contribution of other production modes is substantial, and therefore must be included for a precise theory prediction of this observable.
Different approaches are used for the calculation of the SM-like Higgs boson mass in the MSSM: the fixed-order diagrammatic approach is accurate for low SUSY scales; the EFT approach,for high SUSY scales. Hybrid approaches, combining fixed-order and
EFT calculations, allow to obtain a precise prediction also for intermediary SUSY scales. Here, we briefly discuss the hybrid approach implemented into the code FeynHiggs. In addition, we show how the refined Higgs mass prediction was used to define new MSSM Higgs benchmark scenarios.
A small Higgs mass parameter m_{h_u}^2 can be insensitive to various trial heavy stop masses, if a universal soft squared mass is assumed for the chiral superpartners and the Higgs boson at the grand unification (GUT) scale, and a focus point (FP) of
m_{h_u}^2 appears around the stop mass scale. The challenges in the FP scenario are (1) a too heavy stop mass (~ 5 TeV) needed for the 126 GeV Higgs mass and (2) the too high gluino mass bound (> 1.4 TeV). For a successful FP scenario, we consider (1) a superheavy right-hand (RH) neutrino and (2) the first and second generations of hierarchically heavier chiral superpartners. The RH neutrino can move a FP in the higher energy direction in the space of (Q, m_{h_u}^2(Q)), where Q denotes the renormalization scale. On the other hand, the hierarchically heavier chiral superpartners can lift up a FP in that space through two-loop gauge interactions. Precise focusing of m_{h_u}^2(Q) is achieved with the RH neutrino mass of ~ 10^{14} GeV together with an order one (0.9-1.2) Dirac Yukawa coupling to the Higgs boson, and the hierarchically heavy masses of 15-20 TeV for the heavier generations of superpartners, when the U(1)_R breaking soft parameters, m_{1/2} and A_0 are set to be 1 TeV at the GUT scale. Those values can naturally explain the small neutrino mass through the seesaw mechanism, and suppress the flavor violating processes in supersymmetric models.
The angular distributions of lepton pairs in the Drell-Yan process can provide rich information on the underlying QCD production mechanisms. These dynamics can be parameterised in terms of a set of frame dependent angular coefficients, $A_{i=0,ldots,
7}$, which depend on the invariant mass, transverse momentum, and rapidity of the lepton pair. Motivated by recent measurements of these coefficients by ATLAS and CMS, and in particular by the apparent violation of the Lam-Tung relation $A_0-A_2=0$, we perform a precision study of the angular coefficients at $mathcal{O}(alpha_s^3)$ in perturbative QCD. We make predictions relevant for $pp$ collisions at $sqrt{s} = 8$ TeV, and perform comparisons with the available ATLAS and CMS data as well as providing predictions for a prospective measurement at LHCb. To expose the violation of the Lam-Tung relationship we propose a new observable $Delta^mathrm{LT} = 1-A_2/A_0$ that is more sensitive to the dynamics in the region where $A_0$ and $A_2$ are both small. We find that the $mathcal{O}(alpha_s^3)$ corrections have an important impact on the $p_{T,Z}$ distributions for several of the angular coefficients, and are essential to provide an adequate description of the data. The compatibility of the available ATLAS and CMS data is reassessed by performing a partial $chi^2$ test with respect to the central theoretical prediction which shows that $chi^2/N_mathrm{data}$ is significantly reduced by going from $mathcal{O}(alpha_s^2)$ to $mathcal{O}(alpha_s^3)$.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
