Scalar Bottom Quarks Research Articles

Search for third-generation leptoquarks and scalar bottom quarks in pp collisions at $ \sqrt{s}=7\;TeV $

Abstract Results are presented from a search for third-generation leptoquarks and scalar bottom quarks in a sample of proton-proton collisions at $ \sqrt{s}=7\;TeV $ collected by the CMS experiment at the LHC, corresponding to an integrated luminosity of 4.7 fb−1. A scenario where the new particles are pair produced and each decays to a b quark plus a tau neutrino or neutralino is considered. The number of observed events is found to be in agreement with the standard model prediction. Upper limits are set at 95% confidence level on the production cross sections. Leptoquarks with masses below ~450 GeV are excluded. Upper limits in the mass plane of the scalar quark and neutralino are set such that scalar bottom quark masses up to 410 GeV are excluded for neutralino masses of 50 GeV.

Light neutralino dark matter in the pMSSM

Three dark matter direct detection experiments have reported possible signals which can be interpreted as due to the interaction of light WIMPs with large scattering cross section. In this paper we investigate the viability of SUSY scenarios with light neutralino using high statistics scans in the pMSSM. We identify several scenarios which give rise to very light neutralinos with large direct detection scattering cross sections. We apply constraints from dark matter relic density, direct detection, indirect detection, as well as flavour physics, electroweak precision tests, LEP and Tevatron limits, LHC limits on SUSY, Higgs and monojet searches. In particular we require the Higgs boson mass to be in the range 122.5<M h <127.5 GeV. We study how the combination of these constraints largely reduces the number of viable scenarios. MSSM solutions with a light neutralino and an almost degenerate lightest scalar bottom quark emerge as the scenario in agreement with all these constraints. We study their characteristics in relation to the LHC missing E T searches.

Search for scalar bottom quarks and third-generation leptoquarks in [formula omitted] collisions at [formula omitted

We report the results of a search for pair production of scalar bottom quarks (b˜1) and scalar third-generation leptoquarks (LQ3) in 5.2 fb−1 of pp¯ collisions at the D0 experiment of the Fermilab Tevatron Collider. Scalar bottom quarks are assumed to decay to a neutralino (χ˜10) and a b quark, and we set 95% C.L. lower limits on their production in the (mb˜1, mχ˜10) mass plane such as mb˜1>247 GeV for mχ˜10=0 and mχ˜10>110 GeV for 160<mb˜1<200 GeV. The leptoquarks are assumed to decay to a tau neutrino and a b quark, and we set a 95% C.L. lower limit of 247 GeV on the mass of a charge-1/3 third-generation scalar leptoquark.

Search for the Production of Scalar Bottom Quarks inpp¯Collisions ats=1.96 TeV

We report on a search for direct scalar bottom quark (sbottom) pair production in $p \bar{p}$ collisions at $\sqrt{s}=1.96$~TeV, in events with large missing transverse energy and two jets of hadrons in the final state, where at least one of the jets is required to be identified as originating from a $b$ quark. The study uses a CDF Run~II data sample corresponding to 2.65~fb${}^{-1}$ of integrated luminosity. The data are in agreement with the standard model. In an R-parity conserving minimal supersymmetric scenario, and assuming that the sbottom decays exclusively into a bottom quark and a neutralino, 95$\%$ confidence-level upper limits on the sbottom pair production cross section of 0.1~pb are obtained. For neutralino masses below 70~GeV/$c^2$, sbottom masses up to 230~GeV/$c^2$ are excluded at 95$\%$ confidence level.

Search for Pair Production of Scalar Bottom Quarks inpp¯Collisions ats=1.96 TeV

A search for direct production of scalar bottom quarks (b) is performed with 310 pb(-1) of data collected by the D0 experiment in pp collisions at square root s = 1.96 TeV at the Fermilab Tevatron Collider. The topology analyzed consists of two b jets and an imbalance in transverse momentum due to undetected neutralinos (chi(1)0), with chi(1)0 assumed to be the lightest supersymmetric particle. We find the data consistent with standard model expectations, and set a 95% C.L. exclusion domain in the (m(b), m(chi(1)0)) mass plane, improving significantly upon the results from run I of the Tevatron.

Search for Scalar Bottom Quarks from Gluino Decays inp¯pCollisions ats=1.96 TeV

We searched for scalar bottom quarks in 156 pb$^{-1}$ of {\bf $\bar{p}p$} collisions at {\bf $\sqrt{s}=1.96$} TeV recorded by the CDF II experiment at the Tevatron. Scalar bottom quarks can be produced from gluino decays in R-parity conserving models of supersymmetry when the mass of the gluino exceeds that of the scalar bottom quark. Then, a scalar bottom quark can decay into a bottom quark and a neutralino. To search for this scenario, we investigated events with large missing transverse energy and at least three jets, two or more of which were identified as containing a secondary vertex from the hadronization of $b$ quarks. We found four candidate events, where $2.6\pm 0.7$ are expected from standard model processes, and placed 95% confidence level lower limits on gluino and scalar bottom quark masses of up to 280 and $240\gevm$, respectively.

Neutral Higgs boson masses of the MSSM at the one-loop level in an explicitCPviolation scenario

The neutral Higgs sector of the minimal supersymmetric standard model (MSSM) in explicit CP violation scenario is investigated at the one-loop level. Within the context of the effective potential formalism, the masses of the neutral Higgs bosons are calculated at the one-loop level by taking into account the contributions of the following loops of ordinary particles and superpartners: top quark, the scalar top quarks, bottom quark, the scalar bottom quarks, tau lepton, the scalar tau leptons, $W$ boson, the charged Higgs boson, the charginos, $Z$ boson, the scalar and pseudoscalar Higgs bosons, and the neutralinos. Our calculation is an improvement in the sense that both the terms which are quartic in the electroweak coupling constants into account, and the pseudoscalar Higgs loop contribution are explicitly included.

Search for scalar top and scalar bottom quarks at LEP

Searches for a scalar top quark and a scalar bottom quark have been performed using a data sample of 438 pb−1 at centre-of-mass energies of s=192–209 GeV collected with the OPAL detector at LEP. No evidence for a signal was found. The 95% confidence level lower limit on the scalar top quark mass is 97.6 GeV if the mixing angle between the supersymmetric partners of the left- and right-handed states of the top quark is zero. When the scalar top quark decouples from the Z0 boson, the lower limit is 95.7 GeV. These limits were obtained assuming that the scalar top quark decays into a charm quark and the lightest neutralino, and that the mass difference between the scalar top quark and the lightest neutralino is larger than 10 GeV. The complementary decay mode of the scalar top quark decaying into a bottom quark, a charged lepton and a scalar neutrino has also been studied. The lower limit on the scalar top quark mass is 96.0 GeV for this decay mode, if the mass difference between the scalar top quark and the scalar neutrino is greater than 10 GeV and if the mixing angle of the scalar top quark is zero. From a search for the scalar bottom quark, a mass limit of 96.9 GeV was obtained if the mass difference between the scalar bottom quark and the lightest neutralino is larger than 10 GeV.

Search for scalar quarks in e +e − collisions at [formula omitted] up to 209 GeV

Searches for scalar top, scalar bottom and mass-degenerate scalar quarks are performed in the data collected by the ALEPH detector at LEP, at centre-of-mass energies up to 209 GeV, corresponding to an integrated luminosity of 675 pb −1. No evidence for the production of such particles is found in the decay channels t ̃ → c/ uχ , t ̃ → bℓ ν ̃ , b ̃ → bχ , q ̃ → qχ or in the stop four-body decay channel t ̃ → bχ f f ̄ ′ studied for the first time at LEP. The results of these searches yield improved mass lower limits. In particular, an absolute lower limit of 63 GeV/ c 2 is obtained for the stop mass, at 95% confidence level, irrespective of the stop lifetime and decay branching ratios.

SEARCH FOR SUSY WITH $/\kern-7.2pt E_T$ AND JETS AT CDF

Events with signatures involving large missing transverse energy [Formula: see text] are among the quintessential search modes for R-parity conserving supersymmetry. CDF has conducted two recent analyses for supersymmetry which use [Formula: see text] and jets. The [Formula: see text] and monojet signature is employed to determine process independent limits for the production of new physics beyond the Standard Model and then applied to models of spontaneous breaking of supersymmetry to determine limits on the supersymmetry breaking parameter and the gravitino mass. Direct searches for scalar top and scalar bottom quarks within the framework of supersymmetric models are performed using a signature of [Formula: see text] and two heavy flavor jets. Since the data is found to be consistent with Standard Model expectations, limits are determined in the mass planes [Formula: see text] and [Formula: see text].

Do electroweak precision data and Higgs-mass constraints rule out a scalar bottom quark with mass of order 5 GeV?

We study the implications of a scalar bottom quark, with a mass of O (5 GeV), within the minimal supersymmetric standard model. Light sbottoms may naturally appear for large tan(beta) and, depending on the decay modes, may have escaped experimental detection. We show that a light sbottom cannot be ruled out by electroweak precision data and the bound on the lightest CP-even Higgs-boson mass. We infer that a light b scenario requires a relatively light scalar top quark whose mass is typically about the top-quark mass. In this scenario the lightest Higgs boson decays predominantly into b pairs and obeys the mass bound m(h) less, similar 123 GeV.

Search for a scalar bottom quark with mass 3.5–4.5GeV/c2

We report on a search for a supersymmetric $\tilde{B}$ meson with mass between 3.5 and 4.5 GeV/$c^2$ using 4.52 ${\rm fb}^{-1}$ of integrated luminosity produced at $\sqrt{s}=10.52$ GeV, just below the $e^+e^-\to B\bar{B}$ threshold, and collected with the CLEO detector. We find no evidence for a light scalar bottom quark.

Single sbottom/scharm production at HERA in an R-parity breaking supersymmetric model

We investigate the production process of the single scalar bottom quark (sbottom) and scalar charm quark (scharm) at HERA. The sbottom and scharm could be produced via an R-parity breaking interactions λ′ 123≠0 in the Minimal Supersymmetric Standard Model (MSSM). These processes give a slight excess in the invariant mass M eq distribution of the high Q 2 deep inelastic scattering for sufficiently heavy gauginos and the scalar top (stop). For the light gauginos and stop, it is shown that the tagging of b/ c-quarks and charged leptons with high transverse energies will be indispensable to search for the processes.

Search for scalar top and scalar bottom quarks in pp collisions at square root s=1.8 TeV.

We have searched for direct pair production of scalar top and scalar bottom quarks in 88 pb-1 of pp collisions at sqrt[s]=1.8 TeV with the CDF detector. We looked for events with a pair of heavy flavor jets and missing energy, consistent with scalar top (bottom) quark decays to a charm (bottom) quark and a neutralino. The numbers of events that pass our selections show no significant deviation from standard model expectations. We compare our results to the next-to-leading order scalar quark production cross sections to exclude regions in scalar quark-neutralino mass parameter space.

Additional two-loop contributions to electric dipole moments in supersymmetric theories

We calculate the two-loop contributions to the electric dipole moments of the electron and the neutron mediated by charged Higgs in a generic supersymmetric theories. The new contributions are originated from the potential CP violation in the trilinear couplings of the charged Higgs bosons to the scalar-top or the scalar-bottom quarks. These couplings did not receive stringent constraints directly. We find observable effects for a sizable portion of the parameter space related to the third generation scalar-quarks in the minimal supersymmetric standard model.

Searches for scalar quarks in e +e − interactions at [formula omitted] GeV

Searches for scalar top and scalar bottom quarks, as well as for mass-degenerate scalar quarks of the first two families are performed at 189 GeV centre-of-mass energy with the L3 detector at LEP. No signals are observed. Model-independent limits on the scalar top production cross sections are determined for the decay modes t ̃ 1 → c χ ̃ 1 0 and t ̃ 1 → bℓ ν ̃ . For scalar quarks of the other flavours q ̃ → q χ ̃ 1 0 decays are considered. Within the framework of the Minimal Supersymmetric Standard Model mass limits are set at 95% C.L. for these particles. Indirect limits on the gluino mass are also derived.

Search for scalar top and scalar bottom quarks at [formula omitted] = 189 GeV at LEP

Searches for a scalar top quark and a scalar bottom quark have been performed using a data sample of 182 pb −1 at a centre-of-mass energy of s = 189 GeV collected with the OPAL detector at LEP. No evidence for a signal was found. The 95% confidence level (C.L.) lower limit on the scalar top quark mass is 90.3 GeV if the mixing angle between the supersymmetric partners of the left- and right-handed states of the top quark is zero. In the worst case, when the scalar top quark decouples from the Z 0 boson, the lower limit is 87.2 GeV. These limits were obtained assuming that the scalar top quark decays into a charm quark and the lightest neutralino, and that the mass difference between the scalar top quark and the lightest neutralino is larger than 10 GeV. The complementary decay mode of the scalar top quark decaying into a bottom quark, a charged lepton and a scalar neutrino has also been studied. From a search for the scalar bottom quark, a mass limit of 88.6 GeV was obtained if the mass difference between the scalar bottom quark and the lightest neutralino is larger than 7 GeV. These limits significantly improve the previous OPAL limits.

New Two-Loop Contribution to Electric Dipole Moments in Supersymmetric Theories

We calculate a new type of two-loop contribution to the electric dipole moments of the electron and neutron in supersymmetric theories. The new contributions are originated from the potential $\mathrm{CP}$ violation in the trilinear couplings of the Higgs bosons to the scalar-top or the scalar-bottom quarks. These couplings did not receive stringent constraints directly. The electric dipole moments are induced through a mechanism analogous to that due to Barr and Zee [Phys. Rev. Lett. 65, 21 (1990)]. We find observable effects for a sizable portion of the parameter space related to the third generation scalar quarks in the minimal supersymmetric standard model which cannot be excluded by earlier considerations.

Search for scalar top and scalar bottom quarks at $\sqrt{s}$ = 183 GeV at LEP

Searches for a scalar top quark and a scalar bottom quark have been performed using a total data sample of 56.8 pb\(^{-1}\) at a centre-of-mass energy of \(\sqrt{s} = \)183 GeV collected with the OPAL detector at LEP. No candidate events were observed. Combining this result with those obtained at lower centre-of-mass energies, the 95% C.L. lower limit on the scalar top quark mass is 85.0 GeV if the mixing angle between the supersymmetric partners of the left- and right-handed states of the top quark is zero. The lower limit is 81.3 GeV, even if the scalar top quark decouples from the \({\mathrm Z}^{0}\) boson. These limits were obtained assuming that the scalar top quark decays into a charm quark and the lightest neutralino, and that the mass difference between the scalar top quark and the lightest neutralino is larger than 10 GeV. The complementary decay mode of the scalar top quark in which it decays into a bottom quark, a charged lepton and a scalar neutrino was also studied. From a similar analysis, a mass limit on the light scalar bottom quark was set at 82.7 GeV for a mass difference between the scalar bottom quark and the lightest neutralino larger than 7 GeV, and at 84.0 GeV for the mass difference larger 10 GeV and the lightest neutralino heavier than 30 GeV. These limits were obtained assuming that the scalar bottom quark decays into a bottom quark and the lightest neutralino, and that a mixing angle between the supersymmetric partners of the left- and right-handed states of the bottom quark is zero.

Search for scalar top and scalar bottom quarks at

Searches for a scalar top quark and a scalar bottom quark have been performed using a total data sample of 56.8 pb $^{-1}$ at a centre-of-mass energy of $\sqrt{s} = $ 183 GeV collected with the OPAL detector at LEP. No candidate events were observed. Combining this result with those obtained at lower centre-of-mass energies, the 95% C.L. lower limit on the scalar top quark mass is 85.0 GeV if the mixing angle between the supersymmetric partners of the left- and right-handed states of the top quark is zero. The lower limit is 81.3 GeV, even if the scalar top quark decouples from the ${\mathrm Z}^{0}$ boson. These limits were obtained assuming that the scalar top quark decays into a charm quark and the lightest neutralino, and that the mass difference between the scalar top quark and the lightest neutralino is larger than 10 GeV. The complementary decay mode of the scalar top quark in which it decays into a bottom quark, a charged lepton and a scalar neutrino was also studied. From a similar analysis, a mass limit on the light scalar bottom quark was set at 82.7 GeV for a mass difference between the scalar bottom quark and the lightest neutralino larger than 7 GeV, and at 84.0 GeV for the mass difference larger 10 GeV and the lightest neutralino heavier than 30 GeV. These limits were obtained assuming that the scalar bottom quark decays into a bottom quark and the lightest neutralino, and that a mixing angle between the supersymmetric partners of the left- and right-handed states of the bottom quark is zero.