اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدRadiative Neutralino Production in Low Energy Supersymmetric Models
54
0
0.0
(
0
)
تأليف
Rahul Basu
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
We study the production of the lightest neutralinos in the radiative process $e^+e^- to tildechi^0_1 tildechi^0_1gamma$ in low energy supersymmetric models for the International Linear Collider energies. This includes the minimal supersymmetric standard model as well as its extension with an additional chiral Higgs singlet superfield, the nonminimal supersymmetric standard model. We compare and contrast the dependence of the signal cross section on the parameters of the neutralino sector of the minimal and nonminimal supersymmetric standard model. We also consider the background to this process coming from the Standard Model process $e^+e^- to u bar u gamma$, as well as from the radiative production of the scalar partners of the neutrinos (sneutrinos) $e^+e^- to tilde u tilde u^ast gamma$, which can be a background to the radiative neutralino production when the sneutrinos decay invisibly. In low energy supersymmetric models radiative production of the lightest neutralinos may be the only channel to study supersymmetric partners of the Standard Model particles at the first stage of a linear collider, since heavier neutralinos, charginos and sleptons may be too heavy to be pair-produced at a $e^+ e^-$ machine with $sqrt{s} =500GeV$.
قيم البحث
اقرأ أيضاً
We consider supersymmetric (SUSY) models wherein the strong CP problem is solved by the Peccei-Quinn (PQ) mechanism with a concommitant axion/axino supermultiplet. We examine R-parity conserving models where the neutralino is the lightest SUSY partic
le, so that a mixture of neutralinos and axions serve as cold dark matter. The mixed axion/neutralino CDM scenario can match the measured dark matter abundance for SUSY models which typically give too low a value of the usual thermal neutralino abundance, such as models with wino-like or higgsino-like dark matter. The usual thermal neutralino abundance can be greatly enhanced by the decay of thermally-produced axinos to neutralinos, followed by neutralino re-annihilation at temperatures much lower than freeze-out. In this case, the relic density is usually neutralino dominated, and goes as sim (f_a/N)/m_{axino}^{3/2}. If axino decay occurs before neutralino freeze-out, then instead the neutralino abundance can be augmented by relic axions to match the measured abundance. Entropy production from late-time axino decays can diminish the axion abundance, but ultimately not the neutralino abundance. In mixed axion/neutralino CDM models, it may be possible to detect both a WIMP and an axion as dark matter relics. We also discuss possible modifications of our results due to production and decay of saxions. In the appendices, we present expressions for the Hubble expansion rate and the axion and neutralino relic densities in radiation, matter and decaying-particle dominated universes.
The small CMB amplitude $A_s simeq 10^{-9}$ (or, small temperature fluctuation $delta T/T simeq 10^{-5}$) typically requires an unnaturally small effective coupling of an inflaton $lambda_phi sim 10^{-14}$. In successful models, there usually is extr
a suppression of the amplitude, e.g. by large-field inflaton with non-minimal coupling $xi$, so that $lambda_phi$ can be much larger. But $lambda_phi$ and $xi$ cannot be $sim {cal O}(1)$ simultaneously; the naturalness burden is shared between them. We show that the absence of new physics signals at TeV scale may prefer a more natural size of $xi lesssim {cal O}(1-100)$ with $lambda_phi lesssim {cal O}(10^{-4}-10^{-8})$, constraining larger $xi$ with larger $lambda_phi$ more strongly. This intriguing connection between low- and high-energy physics is made in the scenarios with $U(1)_X$ where inflatons renormalization running also induces Coleman-Weinberg mechanism for the electroweak symmetry breaking. We particularly work out the prospects of LHC 13 and 100 TeV $pp$ colliders for probing the parameter space of the small CMB amplitude.
We study the effects of a non thermal neutralino production, due to the late decay in the early universe of a single modulus field, in the context of the deflected anomaly mediated scenario. In the regime in which the average number of neutralino pro
duced in each modulus decaying process is $bar{N}_{{rm LSP}}ll 1$ also models with a thermal relic density below WMAP data became acceptable models. We find out that these models belong to three different classes with the common feature that the low thermal relic density is entirely due to coannihilation effects. The neutralino annihilation cross section for these classes of models is not particularly high compared with the highest cross sections attainable in the generic framework of the MSSM. Hence the detection prospects either by direct or indirect WIMP search experiments are not encouraging.
We analyze the experimental data from the search for new particles at LEP 100 and obtain mass bounds for the neutralinos of the Next--To--Minimal Supersymmetric Standard Model (NMSSM). We find that for $tanbeta gsim 5.5$ a massless neutralino is stil
l possible, while the lower mass bound for the second lightest neutralino corresponds approximately to that for the lightest neutralino in the Minimal Supersymmetric Standard Model (MSSM).
We examine for representative gaugino-higgsino mixing scenarios sneutrino-neutralino and sneutrino-chargino production in deep inelastic ep-scattering at the cm-energy of 1.8 TeV. The cross sections for sneutrino-chargino production are more than one
order of magnitude bigger than those for sneutrino-squark production. Also for zino-like neutralinos we find cross sections at least comparable to those for sneutrino-squark production.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
