Browsing by Author "Khalil, Shaaban"

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Large BR(h -> tau mu) in supersymmetric models
(Amer Phyical Society, 2017-03-31) Hammad, Ahmed; Khalil, Shaaban; Ün, Cem Salih; Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Fizik Bölümü.; 0000-0002-0595-8803; N-3421-2014; 55325758100
We analyze the lepton flavor-violating (LFV) Higgs decay h -> tau mu in three supersymmetric models: the minimal supersymmetric Standard Model, supersymmetric seesaw model, and supersymmetric B-L model with inverse seesaw (BLSSM-IS). We show that it is not possible to enhance BR(h ->tau mu) without violating the experimental bound on the BRd (tau -> mu gamma) in the generic minimal supersymmetric Standard Model, with nonuniversal slepton masses and/or trilinear couplings. In the supersymmetric seesaw model, where flavor mixing is radiatively generated, the LFV process mu -> e gamma strongly constrains the parameter space, and the maximum value of BR(h -> tau mu) is of order 10(-10), which is much smaller than the recent results reported by the CMS and ATLAS experiments. On the other hand, in the BLSSM-IS with universal soft supersymmetry-breaking terms defined at the grand unified scale, BR(h -> tau mu) can be accommodated in a wide region of the parameter space without violating LFV constraints. Even though the background processes in the LHC have very small cross sections, we also analyze the possible signal within the BLSSM-IS over the relevant background processes and show that a signal can be extracted. The analysis shows that confirmation of the LFV Higgs boson decay reported by CMS and ATLAS would favor the BLSSM-IS class of models.
Lepton flavor violating higgs decays in supersymmetric models
(Amer Inst Physics, 2017) Hammad, Ahmed; Khalil, Shaaban; Akkuş, B.; Öktem, Y.; Doğan, G. S.; Güzelçimen, F.; Ün, Cem Salih; Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Fizik Bölümü.; 0000-0002-0595-8803; N-3421-2014; 55325758100
The ATLAS and CMS collaborations reported the first signal of Lepton Flavor Violating (LFV) Higgs decay into tau and mu leptons. Standard Model forbids such processes at the renormalizable level because of lepton flavor symmetry. On the other hand, many extensions of the Standard Model do not exhibit such a symmetry and the models beyond the Standard Model (BSM) yield such processes. Hence, any signal for LFV processes can be interpreted as a direct probe for the BSM models. In this work, we consider LFV Higgs boson decays in a class of supersymmetric models including minimal supersymmetric extension of the SM (MSSM), Supersymmetric Type I Seesaw, and U(1)(B-L) extended MSSM supplied with the inverse seesaw mechanism for non-zero neutrino masses.
Muon anomalous magnetic moment in SUSY B - L model with inverse seesaw
(Elsevier, 2016-10-17) Khalil, Shaaban; Ün, Cem Salih; Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Fizik Bölümü.; 0000-0002-0595-8803; N-3421-2014; 55325758100
Motivated by the tension between the Higgs mass and muon g - 2 in minimal supersymmetric standard model (MSSM), we analyze the muon g - 2 in supersymmetric B - L extension of the standard model (BLSSM) with inverse seesaw mechanism. In this model, the Higgs mass receives extra important radiative corrections proportional to large neutrino Yukawa coupling. We point out that muon g - 2 also gets significant contribution, due to the constructive interferences of light neutralino effects. The light neutralinos are typically the MSSM Bino like and the supersymmetric partner of U(1)(B-L) gauge boson ((B) over tilde'-ino). We show that with universal soft supersymmetry breaking terms, the muon g-2 resides within 2 sigma of the measured value, namely similar to 20 x 10(-10), with Higgs mass equal to 125 GeV.
Naturalness and dark matter in the supersymmetric B - L extension of the standard model
(Amer Phyical, 2017-09-06) Delle, Rose Luigi; Khalil, Shaaban; King, Simon J. D.; Marzo, Carlo; Moretti, Stefano; Ün, Cem Salih; Uludağ Üniversitesi/Fen Edebiyet Fakültesi/Fizik Bölümü.; 0000-0002-0595-8803; N-3421-2014; 55325758100
We study the naturalness properties of the B - L supersymmetric standard model (BLSSM) with type-I seesaw and compare them to those of the minimal supersymmetric standard model (MSSM) at both low (i.e., Large Hadron Collider) energies and high (i.e., unification) scales. By adopting standard measures of naturalness, we assess that, in the presence of full unification of the additional gauge couplings and scalar/fermionic masses of the BLSSM, such a scenario reveals a somewhat higher degree of fine-tuning (FT) than the MSSM, when the latter is computed at the unification scale and all available theoretical and experimental constraints, but the dark matter (DM) ones, are taken into account. Yet, such a difference, driven primarily by the collider limits requiring a high mass for the gauge boson associated to the breaking of the additional U(1)(B-L) gauge group of the BLSSM in addition to the SU(3)(C) x SU(2)(L) x U(1)(Y) of the MSSM, should be regarded as a modest price to pay for the former in relation to the latter, if one notices that the nonminimal scenario offers a significant volume of parameter space where numerous DM solutions of different compositions can be found to the relic density constraints, unlike the case of the minimal structure, wherein only one type of solution is accessible over an ever diminishing parameter space. In fact, this different level of tension within the two SUSY models in complying with current data is well revealed when the FT measure is recomputed in terms of the low-energy spectra of the two models, over their allowed regions of parameter space now in the presence of all DM bounds, as it is shown that the tendency is now opposite, with the BLSSM appearing more natural than the MSSM.
Prospects for sneutrino dark matter in the blssm
(Soc Italiana Fisica, 2018-07-01) King, Simon J. D.; Delle Rose, Luigi; Khalil, Shaaban; Kulkarni, Suchita; Marzo, Carlo; Moretti, Stefano; Ün, Cem Salih; ÜN, CEM SALİH; Bursa Uludağ Üniversitesi/Fen Edebiyat Fakültesi/Fizik Anabilim Dalı.; N-3421-2014
The (B - L) Supersymmetric Standard Model (BLSSM) motivates several Dark Matter (DM) candidates beyond the Minimally Supersymmetric Standard Model (MSSM). We assess the comparative naturalness of the two models and discuss the potential detection properties of a particular candidate, the Right-Handed (RH) sneutrino.
The 28 gev dimuon excess in lepton specific thdm
(Elsevier, 2022-03-18) Khalil, Shaaban; Cici, Ali; Nis, Büşra; Ün, Cem Salih; ÜN, CEM SALİH; Bursa Uludağ Üniversitesi/Fen Edebiyat Fakültesi/Fizik Bölümü.; 0000-0002-0595-8803; N-3421-2014
We explore the Higgs mass spectrum in a class of Two Higgs Doublet Models (THDMs) in which a scalar SU (2)(L) doublet interacts only with quarks, while the second one interacts only with leptons. The spectrum includes two CP-even Higgs bosons, either of which can account for the SM-like Higgs boson, and the spectra involving light Higgs bosons receive strong impacts from the LEP results and the current collider analyses. We find that a consistent spectrum can involve a CP-odd Higgs boson as light as about 10 GeV, while the lightest CP-even Higgs boson cannot be lighter than about 55 GeV when m(A) similar to 28 GeV. These analyses can rather bound the low tan beta region which can also accommodate an observed excess in dimuon events at m(mu mu) similar to 28 GeV. A lepton-specific class of THDMs (LS-THDM) can predict such an excess through A -> mu mu decays, while the solutions can be constrained by the A -> tau tau mode. After constraining the solutions with the consistent ranges of sigma(pp -> bbA -> bb tau tau), a largest excess at about 1.5 sigma at 8 TeV center of mass (COM) energy and 2 sigma at 13 TeV COM is observed for tan beta similar to 12 and m(A) similar to 28 GeV in the sigma(pp -> bbA -> bb mu mu) events.