XQCAT: eXtra Quark Combined Analysis Tool

Abstract

XQCAT (eXtra Quark Combined Analysis Tool) is a tool aimed at determining exclusion confidence levels for scenarios of new physics characterised by the presence of one or multiple heavy extra quarks which interact through Yukawa couplings with any of the Standard Model quarks. The code uses a database of efficiencies for pre-simulated processes of QCD-induced pair production of extra quarks and their subsequent on-shell decays. In the version 1.2 of XQCAT the efficiencies have been computed for a set of seven publicly available search results by the CMS experiment. The input for the code is a text file in which masses, branching ratios and dominant chirality of the couplings of the new quarks are provided. The output of the code is the exclusion confidence levels of the test point for each implemented experimental analysis considered individually and, when possible, in statistical combination. the Standard Model (SM) with only one XQ representation which couples only to the third generation SM quarks or only to the SM light quark families. In contrast, various theoretically-motivated scenarios of new physics predict a new quark sector, i.e. more than one new quark, with general couplings to SM quarks. Notable examples are composite Higgs models or universal extra-dimensions. Hence, recasting experimental limits for these scenarios can be a challenging task. To avoid time-consuming simulations and dedicated searches for scenarios which can already be excluded by current data, we present a tool for reinterpretation of existing experimental analyses, including those not made for XQs searches, in terms of exclusion confidence levels (eCLs) for XQ models. Our tool should serve as a useful preliminary approach to understand in a quick way the regions of validity of scenarios of new physics. Solution method: The core of the tool consists in a database of pre-simulated efficiencies (ǫ), defined as the ratio of signal events which survive a given set of experimental cuts over the total number of signal events. These efficiencies have been computed simulating the process of pair production and decay of XQs with masses in the range 400-2000 GeV and implementing the selection and kinematics cuts of a set of experimental searches at 7 and 8 TeV. The tool uses the database to reconstruct any scenario where XQs couple to SM quarks through Yukawa interactions and gives as output the eCL of the test point, characterised by values of the XQ masses and their branching ratios (BRs) into specific final Keywords Preprint submitted to Computer Physics CommunicationsSeptember 18, 2015 states, for all the implemented searches. It also provides eCLs for combinations of experimental searches when search bins are uncorrelated. The method has been validated against experimental analyses. Restrictions:The efficiency database has been built under the following hypotheses: QCD-induced pair production of quarks with masses from 400 GeV to 2000 GeV with steps of 100 GeV; the electro-weak ( [7]. The code also relies on the possibility ...

Interplay of vector-like top partner multiplets in a realistic mixing set-up

“…Higher bounds apply in other LHC analyses in the case of specific assumptions on the couplings, for example decay to third generation only. This is however not the case in general when mixing to the light generations is allowed [38,62]. In the following we also consider cases in which the VL quark does not decay to qW .…”

“…Considering the bounds on masses and couplings of the VL multiplets it is possible to compute their branching ratios into SM states, and through the recently developed software XQCAT [38,62,69], one can determine JHEP09(2015)012 the exclusion regions by considering results from dedicated searches in pair production and other searches not specifically designed for VL quarks (such as SUSY analyses). This study can be performed systematically for different combinations of VL multiplets, and we postpone this analysis to a subsequent paper, where we will compare the bounds obtained by XQCAT with dedicated simulations for specific scenarios.…”

Phenomenology of 2HDM with vectorlike quarks

“…As intimated in the Introduction, ATLAS and CMS have performed direct searches for VLQs at 7, 8 TeV, having potential sensitivities up to 800 GeV or so [25,[40][41][42]. We have already explained that several VLQ scenarios may be conceived in order to enable m VLQ values down to 350 GeV or so yet still be compatible with data.…”

A low scale left-right symmetric mirror model

“…(9) can be realized as shown in Fig.3. Vector-like fermions are extensively studied in literature [17,[27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44]].…”