Search Results

You are looking at 1 - 10 of 20 items :

  • "supersymmetric models" x
Clear All


The recent WMAP data have confirmed that exotic dark matter together with the vacuum energy (cosmological constant) dominate in the flat Universe. Modern particle theories provide viable cold dark matter candidates with masses in the GeV-TeV region. All such candidates will be called WIMPs (Weakly Interacting Massive Particles). The nature of dark matter can only be unraveled by its direct detection in the laboratory. In this work we present some theoretical elements relevant to the direct dark matter detection experiments, paying particular attention to directional experiments, i.e. experiments in which not only the energy but the direction of the recoiling nucleus is observed. Since the direction of observation is fixed with respect to the Earth, while the Earth is rotating around its axis, in a directional experiment the angle between the direction of observation and the Sun’s direction of motion will change during the day. So, since the event rates sensitively depend on this angle, the observed signal in such experiments will exhibit very interesting and characteristic periodic diurnal variation.

symmetry "rotations" thus act in some abstract "superspace" with both bosonic (commuting) and fermionic (anti-commuting) coordinates. The analysis of Coleman and Mandula was subsequently generalized and super- seded by the work of Haag, Lopuszanski and Sohnius, who were able to classify all possible supersymmetries of the S matrix [11]. This work is still the basis of all the work done nowadays in supersymmetric model building. According to [11], the most general supersymmetry in four space-time dimensions contains the Poincare algebra, which is generated by the

supergravity multiplet. In the next chapter we shall couple supersymmetric models to super- gravity. We shall find that the chiral superfield R is the Lagrangian of the supergravity multiplet. In Chapter XVII we discovered how to com- pute the components of R. Here we shall use the transformation laws of the chiral and gravity multiplets to derive the same results. We start from the lowest component, R\ = ~M, (20.22) and build the full superfield in analogy with (4.11). From (18.23) we know that <S*| = \ t(<Ja(Jbtab + ib ail/a - ia a$aM). (20.23) XX. NEW 0 VARIABLES AND THE

γ γ signal was reminiscent of the Higgs boson discovery, but the details did not fit well for the particle to be one of the Postscript: Run 2 227 heavy Higgs bosons predicted in supersymmetric models. Perhaps a new and unexpected particle far heavier than anything seen before had been discovered! Over the next several months the theoretical commu- nity worked feverishly to try to explain the new particle. It turned out that it could easily be accomodated as an “add on” to the standard model, to the MSSM, or to a number of other theories, that is, a particle that

. Cosmic ray detectors, such as The Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics (PAMELA) [ 16 ], The Advanced Thin Ionization Calorimeter (ATIC) [ 17 ], Fermi/GLAST [ 18 ] and the Alpha Magnetic Spectrometer (AMS-01, AMS-02) [ 19 , 20 ], which could detect DM indirectly by recording an anomaly in the flux of cosmic rays, have the prospect of detecting DM, if DM annihilates to some set of Standard Model states, see diagram on Fig.1 . Among the WIMP candidates are the Lightest Supersymmetric Particles (LSP), occurring in supersymmetric models

vanishing energy density are supersymmetric ground states of the theory. Such states are ground states because the expectation value of H may never be negative; they are supersymmetric because <0|iJ|0> = 0 implies Q|0> = <2|0> = 0. Ground states of zero energy preserve supersymmetry, while those of positive energy break it spontaneously. This situation is sketched in Figure 8.1. In this chapter we shall discuss three models which exhibit the general properties of spontaneous symmetry breaking in supersymmetric theories. We first consider a supersymmetric model

supersymmetric model the number of free parameters exceeds 100 – not a really elegant or fundamental theory. Moreover, if R-parity (see below) is not conserved, extra free parameters appear. In the absence of R-parity, there are no stable superpartners, i.e. there is no neutralino, which is the proposed SUSY dark matter particle, and the proton loses it stability. If supersymmetry were an exact symmetry in Nature, every fermion of a given mass must have a superpartner boson of the same mass and vice versa. For example, for the electron, there should be a scalar electron

measurements of these terms. To measure them one would need to observe multi-Higgs production: this is further discussed in Djouadi et al (1999) [ 56 ]. In the standard model the Higgs coupling enters by a quartic coupling: however in supersymmetric theories the quartic couplings are connected to gauge couplings which are known, so that in supersymmetric models it is easier to calculate the coefficients. 5.5 What Happens on Long Distance Scales If asymptotic flatness is incorrect then what does happen on long scales? Non-asymptotic flatness introduces the problem of what

p e n d i x 1 for the presence of invisible (or “dark”) matter gravitating around celestial galaxies and clusters; a leading candidate for this dark matter was a neutral, stable particle called the “lightest SUSY particle.”29 In a single, bold, beautiful stroke, supersymmetry provided attractive so- lutions for several intriguing quandaries in physics. Theorists loved it. SUSY theories also required the existence of multiple Higgs bosons. In the simplest versions called “minimal supersymmetric models,” there had to be four additional Higgs bosons, two of them

Vladi- mir Akulov, as well as Yuri Gol’fand and Evgeni Likhtman, From Symmetry Breaking to Supersymmetry 77 had in de pen dently tried out some supersymmetric models, albeit in a rather formal context:7 string theories with one space dimension and abstract generalizations of the algebra of the mathematical structures of relativity. In 1974, Julius Wess and Bruno Zumino at Karlsruhe University developed a four- dimensional supersymmetric theory that later was ex- tended into a realistic particle theory by Zumino and Sergio Ferrara as well as by Howard Georgi and