Handed Fermions Research Articles

Z′ induced forward dominant processes in μTRISTAN experiment

General U(1) extension of the Standard Model (SM) is a well motivated beyond the Standard Model (BSM) scenario where three generations of right handed neutrinos (RHNs) are introduced to cancel gauge and mixed gauge-gravity anomalies. After the U(1)X is broken, RHNs participate in the seesaw mechanism to generate light neutrino masses satisfying neutrino oscillation data. In addition to that, a neutral gauge boson Z′ is evolved which interacts with the left and right handed fermions differently manifesting chiral nature of the model which could be probed in future collider experiments. As a result, if we consider μ+e− and μ+μ+ collisions in μTRISTAN experiment Z′ mediated 2→2 scattering will appear in t− and u-channels depending on the initial and final states being accompanied by the photon and Z mediated interactions. This will result well motivated resulting forward dominant scenarios giving rise to sizable left-right asymmetry. Estimating constraints on general U(1) coupling from LEP-II and LHC for different U(1)X charges, we calculate differential and integrated scattering cross section and left-right asymmetry for μ+e−→μ+e− and μ+μ+→μ+μ+ processes which could be probed at μTRISTAN experiment further enlightening the interaction between Z′ and charged leptons and the U(1)X breaking scale.

Probing left-right symmetry via gravitational waves from domain walls

We study the possibility of probing the scale of left-right symmetry breaking in the context of left-right symmetric models (LRSM). In LRSM, the right handed fermions transform as doublets under a newly introduced $SU(2{)}_{R}$ gauge symmetry. This, along with a discrete parity symmetry $\mathcal{P}$ ensuring identical gauge couplings of left and right sectors make the model left-right symmetric, providing a dynamical origin of parity violation in electroweak interactions via spontaneous symmetry breaking. The spontaneous breaking of $\mathcal{P}$ leads to the formation of domain walls in the early universe. These walls, if made unstable by introducing an explicit parity breaking term, generate gravitational waves (GW) with a spectrum characterized by the wall tension or the spontaneous $\mathcal{P}$ breaking scale, and the explicit $\mathcal{P}$ breaking term. Considering explicit $\mathcal{P}$ breaking terms to originate from Planck suppressed operators provides one-to-one correspondence between the scale of left-right symmetry and sensitivities of near future GW experiments. This is not only complementary to collider and low energy probes of TeV scale LRSM but also to GW generated from first order phase transition in LRSM with different spectral shape, peak frequencies as well as symmetry breaking scales.

Northern Hemisphere UHECR data further supports CMBR photons with weak U(1) component

I further test the theory that the Cosmic Background Radiation (CBR) is made of photons with a weak U(1) component. Tipler (2005) has previously argued that the consistency of the Standard Model (SM) with the Second Law of Thermodynamics requires the early universe CBR to be composed mainly of an SU(2) gauge field. The U(1) field would be suppressed. One of the consequences of this approach is that the Ultra High Energy Cosmic Rays (UHECR) would be able to propagate much further than conventionally accepted, as an SU(2) dominant CBR would be largely unable to couple with right handed fermions. I test if this novel theory solves the problem of UHECR origin by finding suitable candidates up to a redshift z = 0.1 within three degrees of the arrival direction. Utilizing the Fly's Eye Northern Hemisphere UHECR data, I identified candidates with 80% success for the Northern Sky UHECR (98.7% if certain celestial objects which are likely to be Active Galactic Nuclei are absolutely identified as such). This is parsimonious with the CBR theory, which has other important implications for the Standard Model, early universe cosmology, and the origin of matter and anti-matter. This builds off of Tipler and Piasecki (2018), where we have reviewed UHECR data from the Southern Hemisphere to get a 86% success identification rate. We predict that the remaining UHECR not paired with a potential source will have sources identified upon closer telescopic investigations of these regions. Other recent experiments further suggest an SU(2) dominant composition of the CBR photons. The problem of UHECR origin may be solved.

Phenomenology of U(1)_{F} extension of inert-doublet model with exotic scalars and leptons

In this work we will extend the inert-doublet model (IDM) by adding a new U(1)_{F} gauge symmetry to it, under which, a Z_{2} even scalar (phi _{2}) and Z_{2} odd right handed component of two exotic charged leptons (F_{eR}, F_{mu R}), are charged. We also add one Z_{2} even real scalar (phi _{1}) and one complex scalar (phi ), three neutral Majorana right handed fermions (N_{1}, N_{2}, N_{3}), two left handed components of the exotic charged leptons (F_{eL}, F_{mu L}) as well as F_{tau } are all odd under the Z_{2}, all of which are not charged under the U(1)_{F}. With these new particles added to the IDM, we have a model which can give two scalar DM candidates, together they can explain the present DM relic density as well as the muon (g-2) anomaly simultaneously. Also in this model the neutrino masses are generated at one loop level. One of the most peculiar feature of this model is that non-trivial solution to the axial gauge anomaly free conditions lead to the prediction of a stable very heavy partner to the electron (F_{e}), whose present collider limit (13 TeV LHC) on its mass should be around m_{F_{e}} ge few TeV.

Fermion localization in higher curvature spacetime

Fermion localization in a braneworld model in presence of dilaton coupled higher curvature Gauss–Bonnet bulk gravity is discussed. It is shown that the lowest mode of left handed fermions can be naturally localized on the visible brane due to the dilaton coupled higher curvature term without the necessity of any external localizing bulk field.

The Spin‐Charge‐Family Theory Offers Understanding of the Triangle Anomalies Cancellation in the Standard Model

The standard model has for massless quarks and leptons “miraculously” no triangle anomalies due to the fact that the sum of all possible traces T r[τAi τBj τCk] — where , τAi τBj and τCk are the generators of one, of two or of three of the groups SU(3), SU(2) and U(1) — over the representations of one family of the left handed fermions and anti‐fermions (and separately of the right handed fermions and anti‐fermions), contributing to the triangle currents, is equal to zero. It is demonstrated in this paper that this cancellation of the standard model triangle anomaly follows straightforwardly if the SO(3, 1), SU(2), U(1) and SU(3) are the subgroups of the orthogonal group SO(13,1), as it is in the spin‐charge‐family theory. The authors comment on the SO(10) anomaly cancellation, which works if handedness and charges are related “by hand”.

Exploring the top-Higgs FCNC couplings at polarized linear colliders with top spin observables

We study the nature of flavor changing neutral couplings of the top quark with the Higgs boson and the up/charm quark in the toverline{t} production at linear colliders. There are previous bounds on such tqH couplings at both, linear and hadronic colliders, with the assumption that the top couples equally to the left and the right handed fermions. In this paper we examine chirality of the tqH coupling and construct different observables which will be sensitive to it. The kinematics of the emitted q from t → qH in toverline{t} production is discussed and it was found that the polar angle distribution of q is sensitive to the chiral nature of tqH couplings. The observables in the context of top-antitop spin correlations, which are sensitive to new physics in the top decay are considered using different spin-quantization bases. It was found that in particular the off-diagonal basis can be useful to distinguish among the chiral tqH couplings. The sensitivity of the unpolarized ILC in probing the couplings at the 3σ level at sqrt{s}=500 GeV and ℒ = 500 fb−1 is also studied, resulting in predicted BR(t → qH) < 1.19 × 10−3. This limit is further improved to BR(t → qH) < 8.84 × 10−4 with the inclusion of initial beam polarization of left handed electrons and right handed positrons.

Collider signatures of mirror fermions in the framework of a left-right mirror model

The idea of left-right symmetry with mirror fermions is very appealing from the symmetry point of view. In this picture, unlike the Standard Model, the symmetry is not only left-right symmetric, but each left handed fermion multiplet is accompanied by new right handed fermion multiplet of opposite chirality. In this work, we consider a gauge symmetry, $SU(3)_c \otimes SU(2)_L\otimes SU(2)_R \otimes U(1)_{Y^\prime}$ supplemented by a discrete $Z_2$ symmetry. Instead of having right handed multiplets for each left handed multiplets of the same fermions as in the usual left-right model, the mirror model include right handed doublets involving new fermions (called mirrors), and similarly for each right handed singlet, there are corresponding mirror singlets. Thus the gauge anomaly is naturally absent in this model, and the model also provide a solution for the strong CP problem because of parity conservation. The first stage of symmetry breaking is achieved by a doublet mirror Higgs with a vacuum expectation value $\simeq 10^7$ GeV, needed to explain the neutrino mass $\simeq 10^{-11}$ GeV. The mirror fermions can mix with the ordinary fermions via a scalar which is singlet under the gauge symmetry. In this model, only light mirror particles, having masses in the few hundred GeV range are $\hat{e}, \hat{u}, \hat{d}$ with well-defined spectrum. $\hat{u}$ and $\hat{d}$ can be pair produced at the LHC, and can be detected as ($u Z$) and ($d Z$) resonances. We discuss the signals of these mirror fermions at the LHC, and find that the reach at the LHC can be as large as $m_{\hat q}\simeq 800$ GeV.

Effects of Planck scale physics on neutrino mixing parameters in left-right symmetric models

Left right symmetric models (LRSM) are extensions of the standard model by an enlarged gauge group $SU(2)_L \times SU(2)_R \times U(1)_{B-L}$ where automatic inclusion of right handed fermions as $SU(2)_R$ doublets guarantees a natural seesaw origin of neutrino masses. Apart from the extended gauge symmetry, LRSM also has an in-built global discrete symmetry, called D-parity which ensures equal gauge couplings for left and right sectors. Motivated by the fact that global symmetries are expected to be explicitly broken by theories of quantum gravity, here we study the effects of such gravity or Planck scale physics on neutrino masses and mixings by introducing explict D-parity breaking Planck scale suppressed higher dimensional operators. Although such Planck scale suppressd operators have dimension at least six in generic LRSM, dimension five operators can also arise in the presence of additional scalar fields which can be naturally accommodated within SO(10) grand unified theory (GUT) multiplets. We show that, such corrections can give rise to significant changes in the predictions for neutrino mixing parameters from the ones predicted by tree level seesaw formula if the left right symmetry breaking scale is lower than $10^{14}$ GeV.