Pranav Saxena

Bio: Pranav Saxena is an academic researcher from University of Rajasthan. The author has contributed to research in topics: Supersymmetry & Anomaly (physics). The author has an hindex of 2, co-authored 3 publications receiving 6 citations.

Signatures of heavy $Z^\prime$ in the extra U(1) superstring inspired model: RGEs analysis

Abstract: In the extra U(1) superstring inspired model, we examine the electroweak and U(1)-prime symmetry breaking with the singlet and exotic quark D, D+{\c}along with the study of heavy Z-prime boson in accordance with the top quark mass region For this, we have done the analysis of complete renormalization group equations (RGEs)pertaining to the anomaly free E-{\6}-Eta model of rank 5 The Z-prime is found to the order of TeV or above with allowed small Z-Zprime mixing angle, for which the large singlet VEV is required This is done by considering the only non-universality of Yukawa couplings at GUT scale because these do not obey the E-{\6}relationship and also satisfies the unitarity constraints both at GUT and weak scale, where rest of the parameters, ie, gaugino masses, tri-linear couplings, and soft supersymmetric breaking masses are kept universal at GUT scale with the gauge couplings unification The large value of Yukawa couplings (order of 1) triggered the symmetry breaking radiatively and induces the effective-Mu parameter at the electroweak scale and lead to a viable low energy spectrum at weak scale

Low energy theorems and the unitarity bounds in the extra U(1) superstring inspired E 6 models

Abstract: The conventional method using low energy theorems derived by Chanowitz et al. [Phys. Rev. Lett. 57, 2344 (1986);] does not seem to lead to an explicit unitarity limit in the scattering processes of longitudinally polarized gauge bosons for the high energy case in the extra U(1) superstring inspired models, commonly known as {eta} model, emanating from E{sub 6} group of superstring theory. We have made use of an alternative procedure given by Durand and Lopez [Phys. Lett. B 217, 463 (1989);], which is applicable to supersymmetric grand unified theories. Explicit unitarity bounds on the superpotential couplings (identified as Yukawa couplings) are obtained from both using unitarity constraints as well as using renormalization group equations (RGE) analysis at one-loop level utilizing critical couplings concepts implying divergence of scalar coupling at M{sub G}. These are found to be consistent with finiteness over the entire range M{sub Z}{<=}{radical}(s){<=}M{sub G} i.e. from grand unification scale to weak scale. For completeness, the similar approach has been made use of in other models i.e., {chi}, {psi}, and {nu} models emanating from E{sub 6} and it has been noticed that at weak scale, the unitarity bounds on Yukawa couplings do not differ among E{sub 6} extra U(1)more » models significantly except for the case of {chi} model in 16 representations. For the case of the E{sub 6}-{eta} model ({beta}{sub E} congruent with 9.64), the analysis using the unitarity constraints leads to the following bounds on various parameters: {lambda}{sub t(max.)}(M{sub Z})=1.294, {lambda}{sub b(max.)}(M{sub Z})=1.278, {lambda}{sub H(max.)}(M{sub Z})=0.955, {lambda}{sub D(max.)}(M{sub Z})=1.312. The analytical analysis of RGE at the one-loop level provides the following critical bounds on superpotential couplings: {lambda}{sub t,c}(M{sub Z}) congruent with 1.295, {lambda}{sub b,c}(M{sub Z}) congruent with 1.279, {lambda}{sub H,c}(M{sub Z}) congruent with 0.968, {lambda}{sub D,c}(M{sub Z}) congruent with 1.315. Thus superpotential coupling values obtained by both the approaches are in good agreement. Theoretically we have obtained bounds on physical mass parameters using the unitarity constrained superpotential couplings. The bounds are as follows: (i) Absolute upper bound on top quark mass m{sub t}{<=}225 GeV (ii) the upper bound on the lightest neutral Higgs boson mass at the tree level is m{sub H{sub 2}{sup 0}}{sup tree}{<=}169 GeV, and after the inclusion of the one-loop radiative correction it is m{sub H{sub 2}{sup 0}}{<=}229 GeV when {lambda}{sub t}{ne}{lambda}{sub b} at the grand unified theory scale. On the other hand, these are m{sub H{sub 2}{sup 0}}{sup tree}{<=}159 GeV, m{sub H{sub 2}{sup 0}}{<=}222 GeV, respectively, when {lambda}{sub t}={lambda}{sub b} at the grand unified theory scale. A plausible range on D-quark mass as a function of mass scale M{sub Z{sub 2}} is m{sub D}{approx_equal}O(3 TeV) for M{sub Z{sub 2}}{approx_equal}O(1 TeV) for the favored values of tan{beta}{<=}1. The bounds on aforesaid physical parameters in the case of {chi}, {psi}, and {nu} models in the 27 representation are almost identical with those of {eta} model and are consistent with the present day experimental precision measurements.« less

Evaluation of s, t, u parameters, triple gauge boson vertices and some oblique corrections in extra u(1) superstring inspired model

Abstract: Explicit evaluation of the following parameters has been carried out in the extraU (1) superstring inspired model: (i) As Mz2 varies from 555 GeV to 620 GeV and (m t) CDF = 175.6 ± 5.7 GeV (Table 1): (a) SNew varies from -0.100 ± 0.089 to -0.130 ± 0.090, (b) TNew varies from -0.098 ± 0.097 to -0.129 ± 0.098, (c) UNew varies from -0.229 ± 0.177 to -0.253 ± 0.206, (d) Τz varies from 2.487 ± 0.027 to 2.486 ± 0.027, (e) ALR varies from 0.0125 ± 0.0003 to 0.0126 ± 0.0003, (f) A FB b remains constant at 0.0080 ± 0.0007. Almost identical values are obtained for (m t)D0 = 169 GeV (see table 2). (ii) Triple gauge boson vertices (TGV) contributions: AsMz 2 varies from 555 GeV to 620 GeV and (m t) CDF = 175.6 ±5.7 GeV. (a)√s = 500 GeV, asymptotic case: $$\overline f _1^{Z_1 } $$ varies from -0.301 to -0.179; $$\overline f _{3|Z_1 }^{Z_1 } $$ varies from -0.622 to -0.379; $$f_5^{Z_1 } $$ varies from +0.0061 to 0.0056; $$\overline f _{3|Z_1 }^{\gamma _1 } $$ varies from -3.691 to -2.186. $$\overline f _z^{Z_2 } $$ varies from +0.270 to +0.118; $$\overline f _3^{Z_2 } $$ varies from +0.552 to 0.238; $$f_5^{Z_2 } $$ varies from +0.0004 to +0.0002; $$\overline f _{3|Z_2 }^{\gamma _1 } $$ remains constant at -0.110. (b)√s = 700 GeV, asymptotic case: $$\overline f _1^{Z_1 } $$ varies from -0.297 to -0.176; $$\overline f _3^{Z_1 } $$ varies from -0.609 to -0.370; $$\overline f _5^{Z_1 } $$ varies from -0.0082 to -0.0078; $$\overline f _{3|Z_1 }^{\gamma _1 } $$ varies from -3.680 to -2.171.√s = 700 GeV, nonasymptotic case: $$\overline f _1^{Z_2 } $$ varies from -0.173 to -0.299; $$\overline f _3^{Z_2 } $$ varies from-0.343 to -0.591; $$f_5^{Z_2 } $$ varies from -0.005 to -0.011; $$\overline f _{3|Z_2 }^{\gamma _1 } $$ remains constant at -0.110. The pattern of form factors values for√s = 1000, 1200 GeV is almost identical to that of√s= 700 GeV. Further the values of the form factors for (m t)D0 (=169 GeV) follow identical pattern as that of (m t) CDF form factors values (see tables 5, 6, 9, 10). We conclude that the values of all the form factors with the exception of these of $$f_5^{Z_1 } $$ , $$f_5^{Z_2 } $$ are comparable or larger than theS, T values and therefore the TGV contributions are important while deciding the use of extraU (1) model for doing physics beyond standard model.

Minimal Anomalous U(1)' Extension of the MSSM

Abstract: We study an extension of the minimal supersymmetric standard model by an anomalous Abelian vector multiplet and a St\"uckelberg multiplet. The anomalies are cancelled by the Green-Schwarz mechanism and the addition of Chern-Simons terms. The advantage of this choice over the standard one is that it allows for arbitrary values of the quantum numbers of the extra $U(1)$. As a first step toward the study of hadron annihilations producing four leptons in the final state (a clean signal which might be studied at LHC), we then compute the decays ${Z}^{\ensuremath{'}}\ensuremath{\rightarrow}{Z}_{0}\ensuremath{\gamma}$ and ${Z}^{\ensuremath{'}}\ensuremath{\rightarrow}{Z}_{0}{Z}_{0}$. We find that the largest values of the decay rate are $\ensuremath{\sim}{10}^{\ensuremath{-}4}\text{ }\text{ }\mathrm{GeV}$, while the expected number of events per year at LHC is at most of the order of 10.

Neutron Majorana mass from exotic instantons

Abstract: We show how a Majorana mass for the neutron could result from non-perturbative quantum gravity effects peculiar to string theory. In particular, “exotic instantons” in un-oriented string compactifications with D-branes extending the (supersymmetric) standard model could indirectly produce an effective operator δm n t n + h.c.. In a specific model with an extra vector-like pair of ‘quarks’, acquiring a large mass proportional to the string mass scale (exponentially suppressed by a function of the string moduli fields), δm can turn out to be as low as 10−24-10−25 eV. The induced neutron-antineutron oscillations could take place with a time scale τ nn > 108 s that could be tested by the next generation of experiments. On the other hand, proton decay and FCNC’s are automatically strongly suppressed and are compatible with the current experimental limits. Depending on the number of brane intersections, the model may also lead to the generation of Majorana masses for R-handed neutrini. Our proposal could also suggest neutron-neutralino or neutron-axino oscillations, with implications in UCN, Dark Matter Direct Detection, UHECR and Neutron-Antineutron oscillations. This suggests to improve the limits on neutron-antineutron oscillations, as a possible test of string theory and quantum gravity.

Neutron Majorana mass from exotic instantons

Abstract: We show how a Majorana mass for the Neutron could result from non-perturbative quantum gravity effects peculiar to string theory. In particular, "exotic instantons" in un-oriented string compactifications with D-branes extending the (supersymmetric) standard model could indirectly produce an effective operator delta{m} n^t n+h.c. In a specific model with an extra vector-like pair of `quarks', acquiring a large mass proportional to the string mass scale (exponentially suppressed by a function of the string moduli fields), delta{m} can turn out to be as low as 10^{-24}-10^{-25} eV. The induced neutron-antineutron oscillations could take place with a time scale tau_{n\bar{n}} > 10^8 s, that could be tested by the next generation of experiments. On the other hand, proton decay and FCNC's are automatically strongly suppressed and are compatible with the current experimental limits. Depending on the number of brane intersections, the model may also lead to the generation of Majorana masses for R-handed neutrini. Our proposal could also suggest neutron-neutralino or neutron-axino oscillations, with implications in UCN, Dark Matter Direct Detection, UHECR and Neutron-Antineutron oscillations. This suggests to improve the limits on neutron-antineutron oscillations, as a possible test of string theory and quantum gravity.

Gauge Invarience Formulation of Strong WW Scattering

Abstract: Abstract Models of strong WW scattering in the s -wave can be represented in a gauge invariant fashion by defining an effective scalar propagator that represents the strong scattering dynamics. The σ ( qq → qqWW ) signal may then be computed in U-gauge from the complete set of tree amplitudes, just as in the standard model, without using the effective W approximation (EWA). The U-gauge “transcription” has a wider domain of validity than the EWA, and it provides complete distributions for the final state quanta, including experimentally important jet distributions that cannot be obtained from the EWA. Starting from the usual formulation in terms of unphysical Goldstone boson scattering amplitudes, the U-gauge transcription is verified by using BRS invariance to construct the complete set of gauge and Goldstone boson amplitudes in R Σ gauge.

Strong WW scattering in unitary gauge

Abstract: A method to embed models of strong $WW$ scattering in unitary gauge amplitudes is presented that eliminates the need for the effective $W$ approximation (EWA) in the computation of cross sections at high energy colliders.The cross sections obtained from the U-gauge amplitudes include the distributions of the final state fermions in $ff \rightarrow ffWW$, which cannot be obtained from the EWA. Since the U-gauge method preserves the interference of the signal and the gauge sector background amplitudes, which is neglected in the EWA, it is more accurate, especially if the latter is comparable to or bigger than the signal, as occurs for instance at small angles because of Coulomb singularities. The method is illustrated for on-shell $W^+W^+ \rightarrow W^+W^+$ scattering and for $qq \rightarrow qqW^+W^+$.