arXiv subjects

Saeid Paktinat Mehdiabadi

Publications and source records attributed to Saeid Paktinat Mehdiabadi.

9 recordsLinked to original sources

arXiv2024

Vector dark matter and LHC constraints, including a 95 GeV light Higgs boson

We study LHC searches for an extension of the Standard Model (SM) by exploiting an additional Abelian $U_D(1)$ gauge symmetry and a complex scalar Higgs portal. As the scalar is charged under this gauge symmetry, a vector dark matter (VDM) candidate can satisfy the observed relic abundance and limits from direct dark matter (DM) searches. The ATLAS and CMS experiments have developed a broad search program for the DM candidates, including associate production of Higgs boson, $Z$ boson, and top quark that couple to DM. In this paper, we perform an extensive analysis to constrain the model by using these experiments at LHC. It can be seen that the LHC results can exclude some parts of the parameter space that are still allowed by relic density and the direct detection searches. Using the LHC results, all scalar Higgs portal masses are excluded for the light VDM. Furthermore, exclusion limits on the parameter space of the model by using the new results of the CMS and ATLAS Collaborations for a new light Higgs boson with mass $\sim95~\rm GeV$ are provided.

hep-ph↗

arXiv2024

Zh Production, a Tool to Constrain 2HDM

Since the SM Higgs boson, h, is the superposition of two unequal-mass neutral Higgs bosons in 2HDM, therefore the associated production cross section for h and Z in SM and 2HDM can be different. In this paper, the possibility of using this difference to discover or constrain 2HDM is studied. As a main result, the allowed parameter space of 2HDM type-II is found in the light of possible precise measurements from the LHC experiments. It is shown that combination of the constraints from these measurements with the previous constraints on 2HDM, from direct search and flavour physics, can rule out the main part of the 2HDM parameter space.

hep-ph↗

arXiv2022

Parton distribution functions and QCD coupling constant from LHC and non-LHC data

We present a new QCD analysis of parton distribution functions (PDFs) at the next-to-leading order (NLO) and next-to-next-to-leading order (NNLO). In the present paper, the role of special types of experimental measurements for extracting PDFs is investigated and simultaneously the values of the strong coupling constant are determined. Essential elements of this QCD analysis are: the HERA combined data as a base, heavy quark cross section measurement together with Tevatron data on jet production and H1 and ZEUS jet cross sections as "non-LHC" data, and especially the "LHC" data set for top-quark and jet cross sections. These different data sets have allowed detailed information at low $x$, worth information on the nucleon's flavor and have played an important role for some PDFs at large-$x$ and strong coupling constant. Since the large-$x$ gluon PDF benefits from an accurate determination of quark PDFs, we have enough motivation to focus on the top-quark production and jet cross section measurements from LHC to find the impact of these data on the gluon PDF and strong coupling constant. These experimental data have an impact on the relative uncertainties of PDF. The gluon PDF at large-$x$ and the values of $α_s(M_Z^2)$ are affected significantly. Although, the main motivation of this paper is to focus on gluon PDF and also its uncertainty at large-$x$, but notice to heavy PDFs behavior in this region is also very important. We study the intrinsic charm (IC) using BHPS model with together our extracted extrinsic charm PDF at large $x$ which can be very worth for future experiment at the LHC.

hep-ph↗

arXiv2019

Explicit Jet Veto as a Tool to Purify the Underlying Event in the Drell-Yan Process Using CMS Open Data

The underlying event is an important part of high-energy collision events. In the event generators, the underlying event is tuned by fits to collision data. Usually, the underlying event observables are affected by the existence of extra jets and it is difficult to find a part of the phase space which is dominated by the underlying event. In this paper, we suggest to veto the jets in the considered region to disentangle these effects. The idea is verified to work on CMS Open Data. To our knowledge, it is the first time that such ideas are tested on real collision data.

hep-ph↗

arXiv2018

Impact of the top quark cross section data on parton distribution functions

Recent measurements of top quark pair production cross section, which is performed at the LHC and the Tevatron collider, are studied using Hessian profiling technique to obtain their impact on the parton distribution functions (PDFs). The top quark production data covers different center-of-mass energies $\sqrt{s}$= 1.96, 5.02, 7, 8 and 13 TeV in either $pp$ or $p\bar{p}$ collisions. It is explained how the Hessian profiling method may be used to assess the impact of these new data on PDFs and consequently on their predictions. In this research, the impact of recent measurements of top quark pair cross sections on different CT14, MMHT2014, and NNPDF3.0 PDF sets is investigated. The analysis results show that the recent top quark production at the LHC and Tevatron data provide significant constraints in particular on the central value, relative uncertainties or both for the $s$-quark distribution and the gluon PDFs in both of CT14, MMHT2014 PDF sets and are insensitive to valence quark PDFs. A small constraint on the $\bar u$- sea quark distribution for CT14 PDF is also observed. There is no impact on the NNPDF3.0 PDF set in presence of these data.

hep-ph↗

arXiv2018

$W'$ Pair Production in the Light of CMS Searches

For the first time, the pair production of the heavy charged gauge bosons, known as $W'$ bosons is considered, when both decay to $τ$ leptons. The reported detailed efficiency of object/event selection by the CMS experiment is used to find the lower limit on the mass of $W'$ boson. Various assumptions for the coupling of the new gauge boson are examined and the results are reported. In the case of a SM-like $W'$ boson, masses below 290 GeV are excluded at 95\% confidence level. The method can be used to constrain the new models with the similar final state.

hep-ph↗

arXiv2018

The LHC Drell-Yan Measurements as a Constraint for the Noncommutative Space-Time

The LHC measurements of the differential cross section of the Drell-Yan process is used to constrain the noncommutative space-time (NCST) phase space. A $χ^2$ method is utilized to exclude the part of the parameters space which is not consistent with the LHC measurements. Depending on other NCST parameters, the scale can be pushed up to $Λ_{NC} > 655$ GeV. The effect of other parameters is also investigated. To our knowledge, it is the first time that a detailed statistical analysis is performed to compare the NCST results with the Hadron Collider measurements.

hep-ph↗

arXiv2017

The s-Channel Single Top Quark Production as a Constraint for $W'$ Boson Contribution

An analysis is performed to constrain the $W'$ boson production using the measurement of the s-channel single top quark production cross section. Both phenomenological and statistical approaches are examined and results are presented. In the best case, $W'$ bosons that interact only to the right-handed fermions are excluded below 1390 GeV. To our knowledge, it is the first time that the measured cross section of the s-channel single top quark production from the colliders is used to rule out part of the phase space of the $W'$ boson.

hep-ph↗

arXiv2006

Inclusive search for SUSY in top final states at CMS

An inclusive search for low mass SUSY using the top plus missing transverse energy signature at CMS is presented. A 5$σ$ excess can be observed with $\sim$250 pb$^{-1}$ at a particular low mass SUSY point. With the same analysis selection the 5$σ$ discovery reach contours in the mSUGRA parameter space for 1 and 10 fb$^{-1}$ are obtained.

hep-ph↗