arXiv subjects

A. D. Smirnov

Publications and source records attributed to A. D. Smirnov.

At least 19 recordsLinked to original sources

arXiv2020

Chiral gauge leptoquark mass limits and branching ratios of $ K_L^0, B^0, B_s \to l^+_i l^-_j $ decays with account of the general fermion mixing in leptoquark currents

The contributions of the chiral gauge leptoquarks $V^{L,R}$ induced by the chiral four color quark-lepton symmetry to the branching ratios of $ K_L^0, B^0, B_s \to l_1 \, l_2 $ decays are calculated and analysed using the general parametrizations of the fermion mixing matrices in the leptoguark currents. From the current experimental data on these decays under assumption $ m_{V^L} \ll m_{V^R} $ the lower mass limit $ m_{V^L} \cos{γ_L} > 5.68 \,\, \mbox{TeV}$ is found, which in particular case of equal gauge coupling constants gives $ m_{V^L} > 8.03 \,\, \mbox{TeV} $. The branching ratios of the decays under consideration predicted by the chiral gauge leptoquarks are calculated and analysed in dependence on the leptoquark masses and the mixing parameters. It is shown that in consistency with the current experimental data these branching ratios for $ B_s, B^0 \to μe $ decays can be close to their experimental limits and those for $ B_s, B^0 \to τe, τμ$ decays can be of order of~$10^{-7}$. The calculated branching ratios will be useful in the further experimental searches for these decays.

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arXiv2018

Vector leptoquark mass limits and branching ratios of $ K_L^0, B^0, B_s \to l^+_i l^-_j $ decays with account of fermion mixing in leptoquark currents

The contributions of the vector leptoquarks of Pati-Salam type to the branching ratios of $K_L^0, B^0, B_s \to l \, l^{\prime}$ decays are calculated with account of the fermion mixing in the leptoguark currents of the general type. Using the general parametrizations of the mixing matrices the lower vector leptoquark mass limit $ m_V > 86 \,\, TeV $ is found from the current experimental data on these decays. The branching ratios of the decays $B^0, B_s \to l \, l^{\prime}$ predicted at $m_V = 86 \,\, TeV$ are calculated. These branching ratios for the decays $ B^0, B_s \to μ^+ μ^-, e μ$ are close to the experimental data whereas those for the decays $B^0 \to e^+ e^-, e τ, μτ$, and $B_s \to e^+ e^-$ are by order of $2\div4$ less than their current experimental limits. For the decays $B_s \to e τ, μτ$ these branching ratios are of order $10^{-10}$ and $10^{-9}$ respectively. The predicted branching ratios will be usefull in the current and future experimental searches for these decays.

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arXiv2016

Resonance contribution of scalar color octet to $t \bar{t}$ production at the LHC in the minimal four color quark-lepton symmetry model

The scalar color octet contribution to the resonance $t\bar{t}$-pair production at the LHC is calculated and analysed with account of the one loop effective two gluon vertex. It is shown that this contribution from the scalar color octet $F_2$ predicted by the minimal model with the four color quark-lepton symmetry is for $\sqrt{s}=13$ TeV of about a few percents for $750 < m_{F_2} < 1800$ GeV and can exceed 10% for $400 < m_{F_2} < 750$ GeV. It is also pointed out that the search for the scalar octet $F_2$ as the resonance in the dijet mass spectra seems to be difficult because of the smallness of its one loop effective two gluon interaction.

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arXiv2016

Mass limits for the chiral color symmetry $G'$-boson from LHC dijet data

The contributions of $G'$-boson predicted by the chiral color symmetry of quarks to the differential dijet cross-sections in $pp$-collisions at the LHC are calculated and analysed in dependence on two free parameters of the model, the $G'$ mass $m_{G'}$ and mixing angle $θ_G$. The exclusion and consistency $m_{G'}-θ_G$ regions imposed by the ATLAS and CMS data on dijet cross-sections are found. Using the CT10 (MSTW~2008) PDF set we show that the $G'$-boson for $θ_G=45^{\circ}$, i.e. the axigluon, with the masses $m_{G'} < 2.3 \,\, (2.6) \,\, \mbox{TeV}$ and $m_{G'} < 3.35 \,\, (3.25) \,\, \mbox{TeV}$ is excluded at the probability level of $95\%$ by the ATLAS and CMS dijet data respectively. For the other values of $θ_G$ the exclusion limits are more stringent. The $m_{G'}-θ_G$ regions consistent with these data at $CL=68\%$ and $CL=90\%$ are also found.

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arXiv2013

The chiral color symmetry of quarks and $G'$-boson contributions to charge asymmetry in $t \bar t$-production at the LHC and Tevatron

The contributions of $G'$-boson predicted by the chiral color symmetry of quarks to the charge asymmetry $A_C(p p \to t\bar{t})$ in $t \bar{t}$ production at the LHC and to the forward-backward asymmetry $A_{\rm FB}(p\bar{p} \to t\bar{t})$ in $t\bar{t}$ production at the Tevatron are calculated and analysed in dependence on two free parameters of the model, the $G'$ mass $m_{G'}$ and mixing angle $θ_G$. The $m_{G'} - θ_G$ regions of $1 σ$ consistency with the CMS data on the cross section $σ(pp \to t\bar{t})$ and on the charge asymmetry $A_C(p p \to t\bar{t})$ are found and compared with those resulted from the CDF data on the cross section $σ(p\bar{p} \to t\bar{t})$ and on the forward-backward asymmetry $A_{\rm FB}(p\bar{p} \to t\bar{t})$ of $t \bar{t}$ production at the Tevatron with account of the current SM predictions for $A_{\rm FB}(p\bar{p} \to t\bar{t})$.

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arXiv2011

Chiral color symmetry and $G'$-boson mass limit from Tevatron data on $t \bar t$-production

A gauge model with chiral color symmetry of quarks is considered and possible effects of the color $G'$-boson octet predicted by this symmetry are investigated. The contributions of the $G'$-boson to the cross section $σ_{t\bar{t}}$ and to the forward-backward asymmetry $A_{\rm FB}^{p \bar p}$ of $t\bar{t}$ production at the Tevatron are calculated and analysed in dependence on two free parameters of the model, the mixing angle $θ_G$ and $G'$ mass $m_{G'}$. The $G'$-boson contributions to $σ_{t\bar{t}}$ and $A_{\rm FB}^{p \bar p}$ are shown to be consistent with the Tevatron data on $σ_{t\bar{t}}$ and $A_{\rm FB}^{p \bar p}$, the allowed region in the $m_{G'} - θ_G$ plane is discussed and around $m_{G'}=1.2 \, TeV, \; θ_G=14^\circ $ the region of $1 σ$ consistency is found.

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arXiv2011

On mass limit for chiral color symmetry $G'$-boson from Tevatron data on $t \bar{t}$ production

The contributions of $G'$-boson predicted by the chiral color symmetry of quarks to the cross section $σ_{t\bar{t}}$ and to the forward-backward asymmetry $A_{\rm FB}^{p \bar p}$ of $t\bar{t}$ production at the Tevatron are calculated with account of the difference of the strengths of the $\bar q q G$ and $\bar q q G'$ interactions. The results are analysed in dependence on two free parameters of the model, the mixing angle $θ_G$ and $G'$ mass $m_{G'}$. The $G'$-boson contributions to $σ_{t\bar{t}}$ and $A_{\rm FB}^{p \bar p}$ are shown to be consistent with the Tevatron data on $σ_{t\bar{t}}$ and $A_{\rm FB}^{p \bar p}$, the allowed region in the $m_{G'} - θ_G$ plane is discussed and around $m_{G'}=1.2 \, TeV, \; θ_G=14^\circ $ the region of $1 σ$ consistency is found.

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arXiv2010

Cross Section and Forward-Backward Asymmetry of $t\bar{t}$ Production in the Model with Four Color Symmetry

The contributions to the cross section $σ_{t\bar{t}}$ and to the forward-backward asymmetry $A_{\rm FB}^{t \bar t}$ of $t\bar{t}$ production at the Tevatron from $Z'$-boson and scalar leptoquarks $S^{(\pm)}_a$ and scalar gluons $F_a$ predicted by the minimal model with four color quark-lepton symmetry are calculated. These contributions are shown to be small in tree approximation and can be significant with account of the 1-loop $gt\bar{t}$ effective vertex induced by the scalar doublets. The lower mass limit for scalar gluons $m_F \gtrsim 320\, GeV$ from the Tevatron data is obtained and it is shown that for $m_{F_1}\lesssim 990\,GeV$ the scalar gluon $F_1$ can be evident at LHC at the significance not less that $3σ$ (for $\sqrt{s}=14$ TeV, $L=10\,fb^{-1}$).

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arXiv2010

Scalar Leptoquark Contributions into $l_i\to l_jγ$ Processes

The contributions of scalar leptoquarks in lepton flavor violating (LFV) processes of type $l_i\to l_j γ$ are investigated in frame of the minimal model with the four color symmetry and Higgs mechanism of quark and lepton mass generation. It is shown that experimental data on the decays $μ\to e γ$, $τ\to μγ$, $τ\to e γ$ allow the existence of light scalar leptoquarks of type under consideration, with masses of order 1 TeV or below.

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arXiv2009

Chiral color symmetry and possible $G'$-boson effects at the Tevatron and LHC

A gauge model with chiral color symmetry is considered and possible effects of the color $G'$-boson octet predicted by this symmetry are investigated in dependence on two free parameters, the mixing angle $θ_G$ and $G'$ mass $m_{G'}$. The allowed region in the $m_{G'} - θ_G$ plane is found from the Tevatron data on the cross section $σ_{t\bar{t}}$ and forward-backward asymmetry $A_{\rm FB}^{p \bar p}$ of the $t\bar{t}$ production. The mass limits for the $G'$-boson are shown to be stronger than those for the axigluon. A possible effect of the $G'$-boson on the $t\bar{t}$ production at the LHC is discussed and the mass limits providing for the $G'$-boson evidence at the LHC are estimated in dependence on $θ_G$.

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arXiv2009

On a possible manifestation of the four color symmetry $Z'$ boson in $μ^+μ^-$ events at the LHC

The cross section of the $μ^+μ^-$ pair production in $pp$-collisions at the LHC is calculated with acount of the $Z'$ boson induced by the minimal four color quark-lepton symmetry($MQLS$). The $μ^+μ^-$ invariant mass spectrum with account of the $MQLS$ $Z'$ boson is analysed in dependence on the $Z'$ mass. The mass region for the $MQLS$ $Z'$ boson observable at the LHC is found in dependence on the significance and on the integrated luminosity.

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arXiv2008

Colored scalar particles production in $pp$-collisions and possible mass limits for scalar gluons from future LHC data

Cross sections of the colored scalar particle production in $pp$-collisions are calculated and differential and total cross sections of the corresponding parton subprocesses are obtained. The total cross section of scalar gluon production in $pp$-collisions at the LHC is estimated and the dominant decays of scalar gluons are discussed. The production cross section of scalar gluons $F$ with masses $m_F\lesssim 1300$ GeV is shown to be sufficient for the effective production of these particles at the LHC.

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arXiv2007

Mass limits for scalar and gauge leptoquarks from $ K_L^0 \to e^{\mp} μ^{\pm}, B^0 \to e^{\mp} τ^{\pm} $ decays

The contributions of scalar and gauge leptoquarks into widths of $K^0_L \to e^{\mp} μ^{\pm}$, $B^0 \to e^{\mp} τ^{\pm}$ decays are calculated in the models with the vectorlike and chiral four color symmetry and with the Higgs mechanism of the quark-lepton mass splitting. From the current data on $K^0_L$ and $B^0$ decays the mass limits for scalar and chiral leptoquarks and the updated vector leptoquark mass limits are obtained. It is shown that unlike the gauge leptoquarks the scalar leptoquark mass limits are weak, of order or below their direct mass limits. The search for such scalar leptoquarks at LHC and the further search for leptonic decays $ B^0 \to l^+_i l^-_j $ are of interest.

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arXiv2007

On mass limits for leptoquarks from $ K_L^0 \to e^{\mp} μ^{\pm}, B^0 \to e^{\mp} τ^{\pm} $ decays

The contributions of the scalar leptoquark doublets into widths of the $K^0_L \to e^{\mp} μ^{\pm}$, $B^0 \to e^{\mp} τ^{\pm}$ decays are calculated in MQLS model with Higgs mechanism of the quark-lepton mass splitting. The resulted mass limits for the scalar leptoquarks are investigated in comparision with those for vector and chiral gauge leptoquarks. It is shown that the scalar leptoquark mass limits are essentially weaker (about $200 GeV$) than those (a few hundreds $TeV$) for gauge leptoquarks. The search for such scalar leptoquark doublets at LHC and the search for the leptonic decays $ B^0 \to l^+_i l^-_j $ are of interest.

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arXiv2005

Fermionic decays of scalar leptoquarks and scalar gluons in the minimal four color symmetry model

Fermionic decays of the scalar leptoquarks $ S=S_1^{(+)}, S_1^{(-)}, S_m $ and of the scalar gluons $F=F_1, F_2$ predicted by the four color symmetry model with the Higgs mechanism of the quark-lepton mass splitting are investigated. Widths and branching ratios of these decays are calculated and analysed in dependence on coupling constants and on masses of the decaying particles. It is shown that the decays $ S_1^{(+)}\to tl^+_j, S_1^{(-)}\to ν_i\tilde b, S_m\to t\tilde ν_j, F_1\to t\tilde b, F_2\to t\tilde t $ are dominant with the widths of order of a few GeV for $m_S, m_F<1$ TeV and with the total branching ratios close to 1. In the case of $m_S < m_t$ the dominant scalar leptoquark decays are $ S_1^{(+)}\to cl_j^+, S_1^{(-)}\to ν_i\tilde b, S_m\to bł_j^+, S_m\to c\tilde ν_j $ with the total branching ratios $Br(S_1^{(+)}\to cl^+) \approx $ $Br(S_1^{(-)}\to ν\tilde b) \approx 1$, $Br(S_m\to bl^+) \approx 0.9$ and $Br(S_m\to c\tilde ν) \approx 0.1.$ A search for such decays at the LHC and Tevatron may be of interest.

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arXiv2005

Rare t-quark decays $t \to c l_j^{+} l_k^{-}$, $t \to c \tilde{ν_j} ν_k$ in the minimal four color symmetry model

The rare t-quark decays $t \to c l_j^{+} l_k^{-}$, $t \to c \tilde{ν_j} ν_k$ via the scalar leptoquark doublets are investigated in the minimal four color symmetry model with the Higgs mechanism of the quark-lepton mass splitting. The partial widths of these decays are calculated and the total width of the charged lepton mode $ Γ(t \to c {l^{+}}' l^{-})= \sum_{j,k} Γ(t \to c l_{j}^{+} l_{k}^{-})$ and the total width of the neutrino mode $ Γ(t \to c \tildeν' ν)= \sum_{j,k} Γ(t \to c \tilde{ν_{j}} ν_{k})$ are found. The corresponding branching ratios are shown to be $ Br(t \to c {l^{+}}' l^{-}) \approx (3.5 - 0.4) 10^{-5}, $ $ Br(t \to c {\tildeν}' ν) \approx (7.1 - 0.8) 10^{-5} $ for the scalar leptoquark masses $ m_{S}= 180 - 250 GeV $ and for the appropriate values $ (\sinβ \approx 0.2) $ of the mixing angle of the model. The search for such decays at LHC may be of interest.

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arXiv2002

Bounds on scalar leptoquark and scalar gluon masses from current data on S, T, U

The contributions into radiative correction parameters S, T, U from scalar leptoquark and scalar gluon doublets are investigated in the minimal four color symmetry model. It is shown that the existence of the relatively light scalar leptoquarks and scalar gluons (with masses of order of 1 TeV or less) is consistent with the current experimental data on S, T, U and the more light particles (with masses below 400 GeV) improve the fit. In particular, the lightest scalar leptoquarks with masses below 300 GeV are consistent with the current data on S, T, U at $χ^2 < 3.1(3.2)$ for $m_H=115(300) GeV$ in comparison with $χ^2 = 3.5(5.0)$ in the Standard Model. The lightest scalar gluon in this case is expected to lie below $ 850(720) GeV.$ The possible significance of such particles in the t-quark physics at LHC is emphasized and their effect on the gauge coupling constant unification is briefly discussed.

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arXiv2002

Bounds on scalar leptoquark and scalar gluon masses from S, T, U in the minimal four color symmetry model

The contributions into radiative correction parameters S, T, U from scalar leptoquark and scalar gluon doublets are investigated in the minimal four color symmetry model. It is shown that the current experimental data on S, T, U allow the scalar leptoquarks and the scalar gluons to be relatively light (with masses of order of 1 TeV or less), the lightest particles are preferred to lie below 400 GeV. In particular, the lightest scalar leptoquarks with masses below 300 GeV are shown to be compatible with the current data on S, T, U at $χ^2 < 3.1 (3.2)$ for $m_H = 115 (300) GeV$ in comparison with $χ^2 = 3.5 (5.0)$ in the Standard Model. The lightest scalar gluon in this case is expected to lie below 850 (720) GeV. The possible significance of such particles in the t-quark physics at LHC is emphasized.

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