We study $$Z^{\prime }$$ Z ′ phenomenology at hadron colliders in an $$U(1)^{\prime }$$ U ( 1 ) ′... more We study $$Z^{\prime }$$ Z ′ phenomenology at hadron colliders in an $$U(1)^{\prime }$$ U ( 1 ) ′ extended MSSM. We choose a $$U(1)^{\prime }$$ U ( 1 ) ′ model with a secluded sector, where the tension between the electroweak scale and developing a large enough mass for $$Z^{\prime }$$ Z ′ is resolved by incorporating three additional singlet superfields into the model. We perform a detailed analysis of the production, followed by decays, including into supersymmetric particles, of a $$Z^{\prime }$$ Z ′ boson with mass between 4 and 5.2 TeV, with particular emphasis on its possible discovery. We select three different scenarios consistent with the latest available experimental data and relic density constraints, and concentrate on final signals with $$2\ell +\not \! \! E_{T}$$ 2 ℓ + ⧸ E T , $$4\ell +\not \! \! E_{T}$$ 4 ℓ + ⧸ E T and $$6\ell +\not \! \! E_{T}$$ 6 ℓ + ⧸ E T . Including the SM background from processes with two, three or four vector bosons, we show the likelihood of o...
Lorentz and CPT violation in the photon sector with the operators of arbitrary mass dimension has... more Lorentz and CPT violation in the photon sector with the operators of arbitrary mass dimension has been proposed in the context of Standard-Model Extension. The CPT-odd subset of this enlarged model is investigated from a quantum-field theoretical point of view. The generic forms of dispersion relations, polarization vectors and the propagators are obtained for this special subset. Particularly, the general vacuum-orthogonal model is analyzed and it is demonstrated that the vacuum orthogonal model remains vacuum orthogonal at all orders. Although the model has birefringent solutions, they are shown to be spurious. Furthermore, the relevant polarization vectors are shown to be conventional. Leading order model is explicitly analyzed and it is demonstrated that there exists a nontrivial coefficient space satisfying above properties.
We systematically analyze the integrability of a Pauli system in Lorentz violating background at ... more We systematically analyze the integrability of a Pauli system in Lorentz violating background at the non-relativistic level both in two-and three-dimensions. We consider the non-relativistic limit of the Dirac equation from the QED sector of the so-called Standard Model Extension by keeping only two types of background couplings, the vector a µ and the axial vector b µ. We show that the spin-orbit interaction comes as a higher order correction in the non-relativistic limit of the Dirac equation. Such an interaction allows the inclusion of spin degree non-trivially, and if Lorentz violating terms are allowed, they might be comparable under special circumstances. By including all possible first-order derivative terms and considering the cases a = 0, b = 0, and b 0 = 0 one at a time, we determine the possible forms of constants of motion operator, and discuss the existence or continuity of integrability due to Lorentz violating background.
We calculate the one-loop flavor violating top quark decay t → cgg in the Minimal Supersymmetric ... more We calculate the one-loop flavor violating top quark decay t → cgg in the Minimal Supersymmetric Standard Model. We discuss the branching ratios obtained with minimal flavor violation, as well as with soft-supersymmetry induced general flavor violation. Based on this rate we calculate the cross section for the single top quark production via gluon fusion, gg → tc, and evaluate its contribution to the cross section for single top quark production in pp collisions at the Large Hadron Collider. We calculate all contributions coming from the standard model and charged Higgs loops, as well as gluino (and neutralino)-up-type squarks, and chargino-down-type squarks loops. Our numerical results show that the gluino and the chargino contributions are largest over the whole parameter range in the unconstrained Minimal Supersymmetric Standard Model. While in general the gluino contributions dominate the cross section, this result depends on the supersymmetric flavor violating parameters in the up and down squark sector, the relative mass of the gauginos, and whether or not the Grand Unified Theory relationships between gaugino masses are satisfied. In the most promising scenarios, the pp → tc +tc + X cross section at the Large Hadron Collider can reach a few hundreds fb.
We discuss and compare the effects of one extra dimension in the Randall Sundrum models on the ev... more We discuss and compare the effects of one extra dimension in the Randall Sundrum models on the evaluation of the Casimir force between two parallel plates. We impose the condition that the result reproduce the experimental measurements within the known uncertainties in the force and the plate separation, and get an upper bound kR 20 if the curvature parameter k of AdS 5 is equal to the Planck scale. Although the upper bound decreases as k decreases, kR ∼ 12, which is the required value for solving the hierarchy problem, is consistent with the Casimir force measurements. For the case where the 5 th dimension is infinite, the correction to the Casimir force is very small and negligible.
We study the effects of the minimal extension of the standard model including Lorentz violation o... more We study the effects of the minimal extension of the standard model including Lorentz violation on the Casimir force between two parallel conducting plates in vacuum. We provide explicit solutions for the electromagnetic field using scalar field analogy, for both the cases in which the Lorentz violating terms come from the CPT-even or CPT-odd terms. We also calculate the effects of the Lorentz violating terms for a fermion field between two parallel conducting plates and analyze the modifications of the Casimir force due to the modifications of the Dirac equation. In all cases under consideration, the standard formulas for the Casimir force are modified by either multiplicative or additive correction factors, the latter case exhibiting different dependence on the distance between the plates.
The nonzero widths of heavy particles become significant when they appear in the final state of a... more The nonzero widths of heavy particles become significant when they appear in the final state of any decay occurring just around its kinematical threshold. To take into account such effects, a procedure, called the convolution method, was proposed by Altarelli, Conti and Lubicz. We expand their study which included only threshold effects for t → bW Z in the standard model. We discuss finite width effects in the three body decays t → cW W, cZZ and A 0 (h 0) → tbW in the type III version of a two Higgs doublet model. In particular, we find a substantial enhancement in the decay t → cZZ, which brings its branching ratio to BR(t → cZZ) ∼ 10 −3 , and in the decay A 0 → tbW , which, unlike the h 0 case, becomes competitive with the A 0 two-body decay modes.
Motivated by recently observed disagreements with the SM predictions in B decays, we study b → d,... more Motivated by recently observed disagreements with the SM predictions in B decays, we study b → d, s transitions in an asymmetric class of SU (2) L × SU (2) R × U (1) B−L models, with a simple oneparameter structure of the right handed mixing matrix for the quarks, which obeys the constraints from kaon physics. We use experimental constraints on the branching ratios of b → sγ, b → ceν e , and B 0 d,s −B 0 d,s mixing to restrict the parameters of the model: g R /g L , M W 2 , M H ± , tan β as well as the elements of the right-handed quark mixing matrix V R CKM. We present a comparison with the more commonly used (manifest) left-right symmetric model. Our analysis exposes the parameters most sensitive to b transitions and reveals a large parameter space where left-and right-handed quarks mix differently, opening the possibility of observing marked differences in behaviour between the standard model and the left-right model.
With the advent of the LHC, it is important to devise clear tests for Physics Beyond the Standard... more With the advent of the LHC, it is important to devise clear tests for Physics Beyond the Standard Model. Such physics could manifest itself in the form of new charged bosons, whose presence is most naturally occurring in left-right symmetric models (LRSM). We analyze the single W R boson production in an asymmetric left-right model, where the left and right quark mixing matrices are not constrained to be equal. We investigate the cross sections as well as branching ratios of W R bosons at the LHC, including constraints from low energy phenomenology. We then look for most likely signals in pp → W R t → t (dijet) production. Including the background, we find that LHC could show significant signals for the new charged bosons. We compare our results throughout with the manifest left-right symmetric model and comment on similarities and differences.
Colladay and Kostelecký have proposed a framework for studying Lorentz and CPT violation in a nat... more Colladay and Kostelecký have proposed a framework for studying Lorentz and CPT violation in a natural extension of the standard model. Although numerous bounds exist on the Lorentz and CPT violating parameters in the gauge boson and fermion sectors, there are no published bounds on the parameters in the Higgs sector. We determine these bounds. The bounds on the CPT-even asymmetric coefficients arise from the one-loop contributions to the photon propagator, those from the CPT-even symmetric coefficients arise from the equivalent c coefficients in the fermion sector, and those from the CPT-odd coefficient arise from bounds on the vacuum expectation value of the Z boson.
We calculate the one-loop flavor changing neutral current top quark decay t → cgg in the Standard... more We calculate the one-loop flavor changing neutral current top quark decay t → cgg in the Standard Model. We demonstrate that the rate for t → cgg exceeds the rate for a single gluon emission t → cg by about two orders of magnitude, while the rate for t → cqq, q = u is slightly smaller than for t → cg.
Introduction: Mechanical loads can regulate cell proliferation and differentiation at various sta... more Introduction: Mechanical loads can regulate cell proliferation and differentiation at various stages of development and homeostasis. However, the extension of this regulatory effect of mechanical loads on cancer cells is largely unknown. Increased physical compliance is one of the key features of cancer cells, which may hamper the transmission of mechanical loads to these cells within tumor microenvironment. Here we tested whether brief daily application of an external low magnitude mechanical stimulus (LMMS), would impede the growth of MDA-MB-231 aggressive type breast cancer cells in vitro for 3 wks of growth. Methods: The signal was applied in oscillatory form at 90 Hz and 0.15 g, a regimen that would induce mechanical loads on MDA-MB-231 cells via inertial properties of cells rather than matrix deformations. Experimental cells were exposed to LMMS 15 min/day, 5 days/week in ambient conditions while control cells were sham loaded. Cell proliferation, viability, cycle, apoptosis, morphology and migration were tested via Trypan Blue dye exclusion, MTT, PI, Annexin V, Calcein-AM and phalloidin stains and scratch wound assays. Results: Compared to sham controls, daily application of LMMS reduced the number and viability of cancerous MDA-MB-231 cells significantly after first week in the culture, while non-cancerous MCF10A cells were found to be unaffected. Flow cytomety analyses suggested that the observed decrease for the cancer cells in the LMMS group was due to a cell cycle arrest rather than apoptosis. LMMS further reduced cancer cell circularity and increased cytoskeletal actin in MDA-MB-231 cells. Conclusion: Combined, results suggest that direct application of mechanical loads negatively regulate the proliferation of aggressive type cancer cells. If confirmed, this non-invasive approach may be integrated to the efforts for the prevention and/or treatment of cancer.
In light of the recent measurements of the top quark forward-backward asymmetry at the Fermilab T... more In light of the recent measurements of the top quark forward-backward asymmetry at the Fermilab Tevatron experiment, which in some regions of the parameter space shows a discrepancy of 3σ compared to the SM prediction, we analyze top quark pair production and asymmetry in the context of left-right models both at the Tevatron and LHC. We use the minimal manifest left-right model and an asymmetric left-right model where gauge couplings and flavor mixing in the right-handed sector are allowed to differ from those in the left-handed sector. We explore the consequences of including effects from W R and Z R gauge bosons, consistent with phenomenological constraints from meson mixing and new bounds from ATLAS and CMS, for the tt cross section, invariant mass distribution and forward-backward asymmetry at the Tevatron, and predict their values at the LHC. We show that, choosing parameter benchmarks for the model while preserving agreement with collider, electroweak precision, and flavor violation data, the generic left-right model cannot account for the large deviations of the observed asymmetry at the Tevatron and also that it predicts very small charge asymmetries at the LHC.
The neutral fermion sectors of E 6-inspired low energy models, in particular the Alternative Left... more The neutral fermion sectors of E 6-inspired low energy models, in particular the Alternative Left-Right and Inert models, are considered in detail within the non-supersymmetric scenario. We show that in their simplest form, these models always predict, for each generation, the lightest neutrino to be an SU (2) L singlet, as well as two extra neutrinos with masses of the order of the up-quark mass. In order to recover Standard Model phenomenology, additional assumptions in the form of discrete symmetries and/or new interactions are needed. These are classified as the Discrete Symmetry (DS), Higher Dimensional Operators (HDO), and Additional Neutral Fermion (ANF) methods. The DS method can solve the problem, but requires additional Higgs doublets that do not get vacuum expectation values. The HDO method predicts no sterile neutrino, and that the active neutrinos mix with a heavy isodoublet neutrino, thus slightly suppressing the couplings of active neutrinos, with interesting phenomenological implications. The ANF method also predicts this suppression, and also naturally includes one or more "sterile" neutrinos. This scenario allows the existence of sterile neutrino(s) in either a 3 + 1 or 2 + 2 structure at low energies, which are favored by the LSND result.
Several supersymmetric models with extended gauge structures, motivated by either grand unificati... more Several supersymmetric models with extended gauge structures, motivated by either grand unification or by neutrino mass generation, predict light doubly-charged Higgsinos. In this work we study productions and decays of doubly-charged Higgsinos present in left-right supersymmetric models, and show that they invariably lead to novel collider signals not found in the minimal supersymmetric model (MSSM) or in any of its extensions motivated by the µ problem or even in extra dimensional theories. We investigate their distinctive signatures at the Large Hadron Collider (LHC) in both pair-and single-production modes, and show that they are powerful tools in determining the underlying model via the measurements at the LHC experiments.
A sequential fourth generation of quarks and leptons is allowed by precision electroweak constrai... more A sequential fourth generation of quarks and leptons is allowed by precision electroweak constraints if the mass splitting between the heavy quarks is between 50 and 80 GeV. Although heavy quarks can be easily detected at the LHC, it is very difficult to detect a sequential heavy charged lepton, L, due to large backgrounds. Should the L mass be above 250 GeV, it can not be pairproduced at a 500 GeV ILC. We calculate the cross section for the one-loop process e + e − → Lτ. Although the cross section is small, it may be detectable. We also consider contributions from the two Higgs doublet model and the Randall-Sundrum model, in which case the cross section can be substantially higher.
Several supersymmetric models with extended gauge structures, motivated by either grand unificati... more Several supersymmetric models with extended gauge structures, motivated by either grand unification or by neutrino mass generation, predict light doubly-charged Higgsinos. In this work we study the signals of doubly-charged Higgsinos at the Tevatron in both pair-and single-production modes, and show that it is possible, especially from the events containing same-sign same-flavor isolated leptons, to disentangle the effects of doubly-charged Higgsinos in the Tevatron data.
We analyse top quark flavor violating decays into a charm quark and a gluon, photon or Z boson in... more We analyse top quark flavor violating decays into a charm quark and a gluon, photon or Z boson in a supersymmetric model incorporating left-right symmetry. We include loop calculations involving contributions from scalar quarks, gluinos, charginos and neutralinos. We perform the calculations first assuming the minimal (flavor diagonal) scalar quark scenario, and then allowing for arbitrary mixing between the second and third generation of scalar quarks, in both the up and down sectors. In each case we present separately the contributions from gluino, chargino and neutralino loops and compare their respective strengths. In the flavor-diagonal case, the branching ratio cannot exceed 10 −5 (10 −6) for the gluon (photon/Z boson); while for the unconstrained (flavor non-diagonal) case the same branching ratios can reach almost 10 −4 for the gluon, 10 −6 for the photon and 10 −5 for the Z boson, all of which are slightly below the expected reach of LHC.
The extensions of the minimal supersymmetric model (MSSM), driving mainly from the need to solve ... more The extensions of the minimal supersymmetric model (MSSM), driving mainly from the need to solve the problem, involve novel matter species and gauge groups. These extended MSSM models can be searched for at the LHC via the effects of the gauge and Higgs bosons or their fermionic partners. Traditionally, the focus has been on the study of the extra forces induced by the new gauge and Higgs bosons present in such models. An alternative way of studying such effects is through the superpartners of matter species and the gauge forces. We thus consider a Uð1Þ 0 gauge extension of the MSSM, and perform an extensive study of the signatures of the model through the production and decays of the scalar quarks and gluino, which are expected to be produced copiously at the LHC. After a detailed study of the distinctive features of such models with regard to the signatures at the LHC, we carry out a detailed Monte Carlo analysis of the signals from the process pp ! n leptons þ m jets þ E 6 T , and compare the resulting distributions with those predicted by the MSSM. Our results show that the searches for the extra gauge interactions in the supersymmetric framework can proceed not only through the forces mediated by the gauge and Higgs bosons but also through the superpartner forces mediated by the gauge and Higgs fermions. Analysis of the events induced by the squark/gluino decays presented here is complementary to the direct Z 0 searches at the LHC.
We study $$Z^{\prime }$$ Z ′ phenomenology at hadron colliders in an $$U(1)^{\prime }$$ U ( 1 ) ′... more We study $$Z^{\prime }$$ Z ′ phenomenology at hadron colliders in an $$U(1)^{\prime }$$ U ( 1 ) ′ extended MSSM. We choose a $$U(1)^{\prime }$$ U ( 1 ) ′ model with a secluded sector, where the tension between the electroweak scale and developing a large enough mass for $$Z^{\prime }$$ Z ′ is resolved by incorporating three additional singlet superfields into the model. We perform a detailed analysis of the production, followed by decays, including into supersymmetric particles, of a $$Z^{\prime }$$ Z ′ boson with mass between 4 and 5.2 TeV, with particular emphasis on its possible discovery. We select three different scenarios consistent with the latest available experimental data and relic density constraints, and concentrate on final signals with $$2\ell +\not \! \! E_{T}$$ 2 ℓ + ⧸ E T , $$4\ell +\not \! \! E_{T}$$ 4 ℓ + ⧸ E T and $$6\ell +\not \! \! E_{T}$$ 6 ℓ + ⧸ E T . Including the SM background from processes with two, three or four vector bosons, we show the likelihood of o...
Lorentz and CPT violation in the photon sector with the operators of arbitrary mass dimension has... more Lorentz and CPT violation in the photon sector with the operators of arbitrary mass dimension has been proposed in the context of Standard-Model Extension. The CPT-odd subset of this enlarged model is investigated from a quantum-field theoretical point of view. The generic forms of dispersion relations, polarization vectors and the propagators are obtained for this special subset. Particularly, the general vacuum-orthogonal model is analyzed and it is demonstrated that the vacuum orthogonal model remains vacuum orthogonal at all orders. Although the model has birefringent solutions, they are shown to be spurious. Furthermore, the relevant polarization vectors are shown to be conventional. Leading order model is explicitly analyzed and it is demonstrated that there exists a nontrivial coefficient space satisfying above properties.
We systematically analyze the integrability of a Pauli system in Lorentz violating background at ... more We systematically analyze the integrability of a Pauli system in Lorentz violating background at the non-relativistic level both in two-and three-dimensions. We consider the non-relativistic limit of the Dirac equation from the QED sector of the so-called Standard Model Extension by keeping only two types of background couplings, the vector a µ and the axial vector b µ. We show that the spin-orbit interaction comes as a higher order correction in the non-relativistic limit of the Dirac equation. Such an interaction allows the inclusion of spin degree non-trivially, and if Lorentz violating terms are allowed, they might be comparable under special circumstances. By including all possible first-order derivative terms and considering the cases a = 0, b = 0, and b 0 = 0 one at a time, we determine the possible forms of constants of motion operator, and discuss the existence or continuity of integrability due to Lorentz violating background.
We calculate the one-loop flavor violating top quark decay t → cgg in the Minimal Supersymmetric ... more We calculate the one-loop flavor violating top quark decay t → cgg in the Minimal Supersymmetric Standard Model. We discuss the branching ratios obtained with minimal flavor violation, as well as with soft-supersymmetry induced general flavor violation. Based on this rate we calculate the cross section for the single top quark production via gluon fusion, gg → tc, and evaluate its contribution to the cross section for single top quark production in pp collisions at the Large Hadron Collider. We calculate all contributions coming from the standard model and charged Higgs loops, as well as gluino (and neutralino)-up-type squarks, and chargino-down-type squarks loops. Our numerical results show that the gluino and the chargino contributions are largest over the whole parameter range in the unconstrained Minimal Supersymmetric Standard Model. While in general the gluino contributions dominate the cross section, this result depends on the supersymmetric flavor violating parameters in the up and down squark sector, the relative mass of the gauginos, and whether or not the Grand Unified Theory relationships between gaugino masses are satisfied. In the most promising scenarios, the pp → tc +tc + X cross section at the Large Hadron Collider can reach a few hundreds fb.
We discuss and compare the effects of one extra dimension in the Randall Sundrum models on the ev... more We discuss and compare the effects of one extra dimension in the Randall Sundrum models on the evaluation of the Casimir force between two parallel plates. We impose the condition that the result reproduce the experimental measurements within the known uncertainties in the force and the plate separation, and get an upper bound kR 20 if the curvature parameter k of AdS 5 is equal to the Planck scale. Although the upper bound decreases as k decreases, kR ∼ 12, which is the required value for solving the hierarchy problem, is consistent with the Casimir force measurements. For the case where the 5 th dimension is infinite, the correction to the Casimir force is very small and negligible.
We study the effects of the minimal extension of the standard model including Lorentz violation o... more We study the effects of the minimal extension of the standard model including Lorentz violation on the Casimir force between two parallel conducting plates in vacuum. We provide explicit solutions for the electromagnetic field using scalar field analogy, for both the cases in which the Lorentz violating terms come from the CPT-even or CPT-odd terms. We also calculate the effects of the Lorentz violating terms for a fermion field between two parallel conducting plates and analyze the modifications of the Casimir force due to the modifications of the Dirac equation. In all cases under consideration, the standard formulas for the Casimir force are modified by either multiplicative or additive correction factors, the latter case exhibiting different dependence on the distance between the plates.
The nonzero widths of heavy particles become significant when they appear in the final state of a... more The nonzero widths of heavy particles become significant when they appear in the final state of any decay occurring just around its kinematical threshold. To take into account such effects, a procedure, called the convolution method, was proposed by Altarelli, Conti and Lubicz. We expand their study which included only threshold effects for t → bW Z in the standard model. We discuss finite width effects in the three body decays t → cW W, cZZ and A 0 (h 0) → tbW in the type III version of a two Higgs doublet model. In particular, we find a substantial enhancement in the decay t → cZZ, which brings its branching ratio to BR(t → cZZ) ∼ 10 −3 , and in the decay A 0 → tbW , which, unlike the h 0 case, becomes competitive with the A 0 two-body decay modes.
Motivated by recently observed disagreements with the SM predictions in B decays, we study b → d,... more Motivated by recently observed disagreements with the SM predictions in B decays, we study b → d, s transitions in an asymmetric class of SU (2) L × SU (2) R × U (1) B−L models, with a simple oneparameter structure of the right handed mixing matrix for the quarks, which obeys the constraints from kaon physics. We use experimental constraints on the branching ratios of b → sγ, b → ceν e , and B 0 d,s −B 0 d,s mixing to restrict the parameters of the model: g R /g L , M W 2 , M H ± , tan β as well as the elements of the right-handed quark mixing matrix V R CKM. We present a comparison with the more commonly used (manifest) left-right symmetric model. Our analysis exposes the parameters most sensitive to b transitions and reveals a large parameter space where left-and right-handed quarks mix differently, opening the possibility of observing marked differences in behaviour between the standard model and the left-right model.
With the advent of the LHC, it is important to devise clear tests for Physics Beyond the Standard... more With the advent of the LHC, it is important to devise clear tests for Physics Beyond the Standard Model. Such physics could manifest itself in the form of new charged bosons, whose presence is most naturally occurring in left-right symmetric models (LRSM). We analyze the single W R boson production in an asymmetric left-right model, where the left and right quark mixing matrices are not constrained to be equal. We investigate the cross sections as well as branching ratios of W R bosons at the LHC, including constraints from low energy phenomenology. We then look for most likely signals in pp → W R t → t (dijet) production. Including the background, we find that LHC could show significant signals for the new charged bosons. We compare our results throughout with the manifest left-right symmetric model and comment on similarities and differences.
Colladay and Kostelecký have proposed a framework for studying Lorentz and CPT violation in a nat... more Colladay and Kostelecký have proposed a framework for studying Lorentz and CPT violation in a natural extension of the standard model. Although numerous bounds exist on the Lorentz and CPT violating parameters in the gauge boson and fermion sectors, there are no published bounds on the parameters in the Higgs sector. We determine these bounds. The bounds on the CPT-even asymmetric coefficients arise from the one-loop contributions to the photon propagator, those from the CPT-even symmetric coefficients arise from the equivalent c coefficients in the fermion sector, and those from the CPT-odd coefficient arise from bounds on the vacuum expectation value of the Z boson.
We calculate the one-loop flavor changing neutral current top quark decay t → cgg in the Standard... more We calculate the one-loop flavor changing neutral current top quark decay t → cgg in the Standard Model. We demonstrate that the rate for t → cgg exceeds the rate for a single gluon emission t → cg by about two orders of magnitude, while the rate for t → cqq, q = u is slightly smaller than for t → cg.
Introduction: Mechanical loads can regulate cell proliferation and differentiation at various sta... more Introduction: Mechanical loads can regulate cell proliferation and differentiation at various stages of development and homeostasis. However, the extension of this regulatory effect of mechanical loads on cancer cells is largely unknown. Increased physical compliance is one of the key features of cancer cells, which may hamper the transmission of mechanical loads to these cells within tumor microenvironment. Here we tested whether brief daily application of an external low magnitude mechanical stimulus (LMMS), would impede the growth of MDA-MB-231 aggressive type breast cancer cells in vitro for 3 wks of growth. Methods: The signal was applied in oscillatory form at 90 Hz and 0.15 g, a regimen that would induce mechanical loads on MDA-MB-231 cells via inertial properties of cells rather than matrix deformations. Experimental cells were exposed to LMMS 15 min/day, 5 days/week in ambient conditions while control cells were sham loaded. Cell proliferation, viability, cycle, apoptosis, morphology and migration were tested via Trypan Blue dye exclusion, MTT, PI, Annexin V, Calcein-AM and phalloidin stains and scratch wound assays. Results: Compared to sham controls, daily application of LMMS reduced the number and viability of cancerous MDA-MB-231 cells significantly after first week in the culture, while non-cancerous MCF10A cells were found to be unaffected. Flow cytomety analyses suggested that the observed decrease for the cancer cells in the LMMS group was due to a cell cycle arrest rather than apoptosis. LMMS further reduced cancer cell circularity and increased cytoskeletal actin in MDA-MB-231 cells. Conclusion: Combined, results suggest that direct application of mechanical loads negatively regulate the proliferation of aggressive type cancer cells. If confirmed, this non-invasive approach may be integrated to the efforts for the prevention and/or treatment of cancer.
In light of the recent measurements of the top quark forward-backward asymmetry at the Fermilab T... more In light of the recent measurements of the top quark forward-backward asymmetry at the Fermilab Tevatron experiment, which in some regions of the parameter space shows a discrepancy of 3σ compared to the SM prediction, we analyze top quark pair production and asymmetry in the context of left-right models both at the Tevatron and LHC. We use the minimal manifest left-right model and an asymmetric left-right model where gauge couplings and flavor mixing in the right-handed sector are allowed to differ from those in the left-handed sector. We explore the consequences of including effects from W R and Z R gauge bosons, consistent with phenomenological constraints from meson mixing and new bounds from ATLAS and CMS, for the tt cross section, invariant mass distribution and forward-backward asymmetry at the Tevatron, and predict their values at the LHC. We show that, choosing parameter benchmarks for the model while preserving agreement with collider, electroweak precision, and flavor violation data, the generic left-right model cannot account for the large deviations of the observed asymmetry at the Tevatron and also that it predicts very small charge asymmetries at the LHC.
The neutral fermion sectors of E 6-inspired low energy models, in particular the Alternative Left... more The neutral fermion sectors of E 6-inspired low energy models, in particular the Alternative Left-Right and Inert models, are considered in detail within the non-supersymmetric scenario. We show that in their simplest form, these models always predict, for each generation, the lightest neutrino to be an SU (2) L singlet, as well as two extra neutrinos with masses of the order of the up-quark mass. In order to recover Standard Model phenomenology, additional assumptions in the form of discrete symmetries and/or new interactions are needed. These are classified as the Discrete Symmetry (DS), Higher Dimensional Operators (HDO), and Additional Neutral Fermion (ANF) methods. The DS method can solve the problem, but requires additional Higgs doublets that do not get vacuum expectation values. The HDO method predicts no sterile neutrino, and that the active neutrinos mix with a heavy isodoublet neutrino, thus slightly suppressing the couplings of active neutrinos, with interesting phenomenological implications. The ANF method also predicts this suppression, and also naturally includes one or more "sterile" neutrinos. This scenario allows the existence of sterile neutrino(s) in either a 3 + 1 or 2 + 2 structure at low energies, which are favored by the LSND result.
Several supersymmetric models with extended gauge structures, motivated by either grand unificati... more Several supersymmetric models with extended gauge structures, motivated by either grand unification or by neutrino mass generation, predict light doubly-charged Higgsinos. In this work we study productions and decays of doubly-charged Higgsinos present in left-right supersymmetric models, and show that they invariably lead to novel collider signals not found in the minimal supersymmetric model (MSSM) or in any of its extensions motivated by the µ problem or even in extra dimensional theories. We investigate their distinctive signatures at the Large Hadron Collider (LHC) in both pair-and single-production modes, and show that they are powerful tools in determining the underlying model via the measurements at the LHC experiments.
A sequential fourth generation of quarks and leptons is allowed by precision electroweak constrai... more A sequential fourth generation of quarks and leptons is allowed by precision electroweak constraints if the mass splitting between the heavy quarks is between 50 and 80 GeV. Although heavy quarks can be easily detected at the LHC, it is very difficult to detect a sequential heavy charged lepton, L, due to large backgrounds. Should the L mass be above 250 GeV, it can not be pairproduced at a 500 GeV ILC. We calculate the cross section for the one-loop process e + e − → Lτ. Although the cross section is small, it may be detectable. We also consider contributions from the two Higgs doublet model and the Randall-Sundrum model, in which case the cross section can be substantially higher.
Several supersymmetric models with extended gauge structures, motivated by either grand unificati... more Several supersymmetric models with extended gauge structures, motivated by either grand unification or by neutrino mass generation, predict light doubly-charged Higgsinos. In this work we study the signals of doubly-charged Higgsinos at the Tevatron in both pair-and single-production modes, and show that it is possible, especially from the events containing same-sign same-flavor isolated leptons, to disentangle the effects of doubly-charged Higgsinos in the Tevatron data.
We analyse top quark flavor violating decays into a charm quark and a gluon, photon or Z boson in... more We analyse top quark flavor violating decays into a charm quark and a gluon, photon or Z boson in a supersymmetric model incorporating left-right symmetry. We include loop calculations involving contributions from scalar quarks, gluinos, charginos and neutralinos. We perform the calculations first assuming the minimal (flavor diagonal) scalar quark scenario, and then allowing for arbitrary mixing between the second and third generation of scalar quarks, in both the up and down sectors. In each case we present separately the contributions from gluino, chargino and neutralino loops and compare their respective strengths. In the flavor-diagonal case, the branching ratio cannot exceed 10 −5 (10 −6) for the gluon (photon/Z boson); while for the unconstrained (flavor non-diagonal) case the same branching ratios can reach almost 10 −4 for the gluon, 10 −6 for the photon and 10 −5 for the Z boson, all of which are slightly below the expected reach of LHC.
The extensions of the minimal supersymmetric model (MSSM), driving mainly from the need to solve ... more The extensions of the minimal supersymmetric model (MSSM), driving mainly from the need to solve the problem, involve novel matter species and gauge groups. These extended MSSM models can be searched for at the LHC via the effects of the gauge and Higgs bosons or their fermionic partners. Traditionally, the focus has been on the study of the extra forces induced by the new gauge and Higgs bosons present in such models. An alternative way of studying such effects is through the superpartners of matter species and the gauge forces. We thus consider a Uð1Þ 0 gauge extension of the MSSM, and perform an extensive study of the signatures of the model through the production and decays of the scalar quarks and gluino, which are expected to be produced copiously at the LHC. After a detailed study of the distinctive features of such models with regard to the signatures at the LHC, we carry out a detailed Monte Carlo analysis of the signals from the process pp ! n leptons þ m jets þ E 6 T , and compare the resulting distributions with those predicted by the MSSM. Our results show that the searches for the extra gauge interactions in the supersymmetric framework can proceed not only through the forces mediated by the gauge and Higgs bosons but also through the superpartner forces mediated by the gauge and Higgs fermions. Analysis of the events induced by the squark/gluino decays presented here is complementary to the direct Z 0 searches at the LHC.
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Papers by Ismail Turan