اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدPurely flavor-changing Z bosons and where they might hide
74
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
A plethora of ultraviolet completions of the Standard Model have extra U(1) gauge symmetries. In general, the associated massive $Z^prime$ gauge boson can mediate flavor-changing neutral current processes at tree level. We consider a situation where the $Z^prime$ boson couples solely via flavor-changing interactions to quarks and leptons. In this scenario the model parameter space is, in general, quite well constrained by existing flavor bounds. However, we argue that cancellation effects shelter islands in parameter space from strong flavor constraints and that these can be probed by multipurpose collider experiments like ATLAS or CMS as well as LHCb in upcoming runs at the LHC. In still allowed regions of parameter space these scenarios may help to explain the current tension between theory and experiment of $(g-2)_mu$ as well as a small anomaly in $tau$ decays.
قيم البحث
اقرأ أيضاً
Models with a non-universal Z exhibit in general flavor changing neutral currents (FCNC) at tree-level. When the Z couplings favor the third generation, flavor changing transitions of the form Ztc and Ztu could be large enough to be observable at the
LHC. In this paper we explore this possibility using the associated production of a single top-quark with the Z and find that integrated luminosities of a few hundred fb$^{-1}$ are necessary to probe the interesting region of parameter space.
Flavor-changing and CP-violating interactions of Z to fermions are generally present in models with extra U(1) gauge symmetry that are string-inspired or related to broken gauged family symmetry. We study the consequences of such couplings in fermion
electric dipole moments, muon g-2, and K and B meson mixings. From experimental limits or measured values, we constrain the off-diagonal Z couplings to fermions. Some of these constraints are comparable or stronger than the existing constraints obtained from other observables.
Rare $B$ meson decays offer an opportunity to probe a light hidden $Z$ boson. In this work we explore a new channel $B_q to gamma Z$ ($q = d, s$) followed by a cascade decay of $Z$ into an invisible (neutrino or dark matter) or charged lepton pair $e
ll^+ ell^-$ ($ell=e ,mu)$. The study is based on a simplified effective model where the down quark sector has tiny flavor-changing neutral current couplings with $Z$. For the first time, we calculate ${rm BR}(B_q to gamma Z)$ at the leading power of $1/m_b$ and $1/E_gamma$. Confronting with the strong constraints from semi-invisible decays of $B$ meson, we find that the branching ratio for $B_d to {rm invisible} + gamma$ can be larger than its Standard Model prediction, leaving a large room for new physics, in particular for light dark matter. Additionally, the branching ratio for $B_d to e^+ e^- gamma$ can also be sizable when the corresponding flavor violating $Z$ coupling to quarks is of the axial-vector type. On the other hand, the predicted branching ratios of $B_d to mu^+ mu^- gamma$ and $B_s to ell^+ ell^- gamma$ are severely constrained by the experimental measurements.
For centuries extremely-long grazing fireball displays have fascinated observers and inspired people to ponder about their origins. The Desert Fireball Network (DFN) is the largest single fireball network in the world, covering about one third of Aus
tralian skies. This expansive size has enabled us to capture a majority of the atmospheric trajectory of a spectacular grazing event that lasted over90 seconds, penetrated as deep as ~58.5km, and traveled over 1,300 km through the atmosphere before exiting back into interplanetary space. Based on our triangulation and dynamic analyses of the event, we have estimated the initial mass to be at least 60 kg, which would correspond to a30 cm object given a chondritic density (3500 kg m-3). However, this initial mass estimate is likely a lower bound, considering the minimal deceleration observed in the luminous phase. The most intriguing quality of this close encounter is that the meteoroid originated from an Apollo-type orbit and was inserted into a Jupiter-family comet (JFC) orbit due to the net energy gained during the close encounter with the Earth. Based on numerical simulations, the meteoroid will likely spend ~200kyrs on a JFC orbit and have numerous encounters with Jupiter, the first of which will occur in January-March 2025. Eventually the meteoroid will likely be ejected from the Solar System or be flung into a trans-Neptunian orbit.
Simple symmetry arguments applied to the third generation lead to a prediction: there exist new sequential Higgs doublets with masses of order $lesssim 5 $ TeV, with approximately universal Higgs-Yukawa coupling constants, $gsim 1$. This is calibrate
d by the known Higgs boson mass, the top quark Higgs-Yukawa coupling, and the $b$-quark mass. A new massive weak-isodoublet, $H_b$, coupled to the $b$-quark with $gsim 1$ is predicted, and may be accessible to the LHC at $13$ TeV, and definitively at the energy upgraded LHC of $26$ TeV. The extension to leptons generates a new $H_tau$ and a possible $H_{ u_tau}$ doublet. The accessibility of the latter depends upon whether the mass of the $tau$-neutrino is Dirac or Majorana.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
