We consider the possibility of probing left-right symmetric model (LRSM) via cosmic microwave background (CMB). We adopt the minimal LRSM with Higgs doublets, also known as the doublet left-right model (DLRM), where all fermions including the neutrinos acquire masses only via their couplings to the Higgs bidoublet. Due to the Dirac nature of light neutrinos, there exist additional relativistic degrees of freedom which can thermalise in the early universe by virtue of their gauge interactions corresponding to the right sector. We constrain the model from Planck 2018 bound on the effective relativistic degrees of freedom and also estimate the prospects for planned CMB Stage IV experiments to constrain the model further. We find that $W_R$ boson mass below 4.06 TeV can be ruled out from Planck 2018 bound at $2σ$ CL in the exact left-right symmetric limit which is equally competitive as the LHC bounds from dijet resonance searches. On the other hand Planck 2018 bound at $1σ$ CL can rule out a much larger parameter space out of reach of present direct search experiments, even in the presence of additional relativistic degrees of freedom around the TeV corner. We also study the consequence of these constraints on dark matter in DLRM by considering a right handed real fermion quintuplet to be the dominant dark matter component in the universe.
Predictions for hadron polarizations and left-right asymmetry in inclusive reactions involving photons
一个唯象模型，其中有一些成功的解释极化现象和左右不对称的包容性质子-质子散射被认为是涉及光子的反应。特别地，考虑了反应（a）$ γ+ p \to H + X;$（b）$γ+ p (\uparrow) \to π^{\pm} + X $和（c）$p(\uparrow) + p \to γ+ X$，其中$γ=$分辨光子和超子$ H = Λ^0, Σ^{\pm}$等。（a）中超子极化的预测和（b）和（c）中的不对称性提供了对该特定模型的进一步检验。简要讨论了在HERA观测（b）的可行性和海水极化对$p (\uparrow) + p \to π^{\pm} + X$质子的影响。
