To say that this is the best book on the quantum theory of fields is no praise, since to my knowledge it is the only book on this subject But it is a very good and most useful book The original was written in German and appeared in 1942 This is a translation with some minor changes A few remarks have been added, concerning meson theory and nuclear forces, also footnotes referring to modern work in this field, and finally an appendix on the symmetrization of the energy momentum tensor according to Belinfante Quantum Theory of Fields Prof Gregor Wentzel Translated from the German by Charlotte Houtermans and J M Jauch Pp ix + 224, (New York and London: Interscience Publishers, Inc, 1949) 36s

Quantum Theory of Fields

The first 1 fb−1 of LHC searches have set impressive limits on new colored particles decaying to missing energy. We address the implication of these searches for naturalness in supersymmetry (SUSY). General bottom-up considerations of natural electroweak symmetry breaking show that higgsinos, stops, and the gluino should not be too far above the weak scale. The rest of the spectrum, including the squarks of the first two generations, can be heavier and beyond the current LHC reach. We have used collider simulations to determine the limits that all of the 1 fb−1 searches pose on higgsinos, stops, and the gluino. We find that stops and the left-handed sbottom are starting to be constrained and must be heavier than about 200–300 GeV when decaying to higgsinos. The gluino must be heavier than about 600–800 GeV when it decays to stops and sbottoms. While these findings point toward scenarios with a lighter third generation split from the other squarks, we do find that moderately-tuned regions remain, where the gluino is just above 1 TeV and all the squarks are degenerate and light. Among all the searches, jets plus missing energy and same-sign dileptons often provide the most powerful probes of natural SUSY. Overall, our results indicate that natural SUSY has survived the first 1 fb−1 of data. The LHC is now on the brink of exploring the most interesting region of SUSY parameter space.

Natural SUSY Endures

Weak scale supersymmetry is often said to be fine-tuned, especially if the matter content is minimal. This is not true if there is a large A term for the top squarks. We present a systematic study on fine-tuning in minimal supersymmetric theories and identify low-energy spectra that do not lead to severe fine-tuning. Characteristic features of these spectra are: a large A term for the top squarks, small top squark masses, moderately large tan{beta}, and a small {mu} parameter. There are classes of theories leading to these features, which are discussed. In one class, which allows a complete elimination of fine-tuning, the Higgsinos are the lightest among all the superpartners of the standard model particles, leading to three nearly degenerate neutralino/chargino states. This gives interesting signals at the LHC--the dilepton invariant mass distribution has a very small endpoint and shows a particular shape determined by the Higgsino nature of the two lightest neutralinos. We demonstrate that these signals are indeed useful in realistic analyses by performing Monte Carlo simulations, including detector simulations and background estimations. We also present a method that allows the determination of all the relevant superparticle masses without using input from particular models, despite the limited kinematicalmore » information due to short cascades. This allows us to test various possible models, which is demonstrated in the case of a model with mixed moduli-anomaly mediation. We also give a simple derivation of special renormalization group properties associated with moduli mediated supersymmetry-breaking, which are relevant in a model without fine-tuning.« less

/pdf/supersymmetry-naturalness-and-signatures-at-the-lhc-3ulo3gy68s.pdf

Supersymmetry, Naturalness, and Signatures at the LHC

In some string compactifications, for instance the recently proposed KKLT set-up, light moduli are stabilized by nonperturbative effects at supersymmetric AdS vacuum which is lifted to a dS vacuum by supersymmetry breaking uplifting potential. In such models, soft supersymmetry breaking terms are determined by a specific mixed modulus-anomaly mediation in which the two mediations typically give comparable contributions to soft parameters. Similar pattern of soft terms can arise also in brane models to stabilize the radion by nonperturbative effects. We examine some phenomenological consequences of this mixed modulus-anomaly mediation, including the pattern of low energy sparticle spectrum and the possibility of electroweak symmetry breaking. It is noted that adding the anomaly-mediated contributions at MGUT amounts to replacing the messenger scale of the modulus mediation by a mirage messenger scale (m3/2/MPl)?/2MGUT where ? = m3/2/[M0ln (MPl/m3/2)] for M0 denoting the modulus-mediated contribution to the gaugino mass at MGUT. The minimal KKLT set-up predicts ? = 1. As a consequence, for ? = (1), the model can lead to a highly distinctive pattern of sparticle masses at TeV scale, particularly when ? = 2.

https://iopscience.iop.org/article/10.1088/1126-6708/2005/09/039/pdf

Phenomenology of mixed modulus-anomaly mediation in fluxed string compactifications and brane models

We interpret the current experimental limit on the lightest Higgs boson mass to suggest that, if nature is supersymmetric, there are additional interactions beyond those of the minimal supersymmetric standard model (MSSM) coming from new degrees of freedom around the TeV scale. Within an effective field theory analysis, the leading order corrections to the MSSM are described in terms of only two operators. This provides a highly constrained description of beyond MSSM physics. The scalar Higgs spectrum as well as the chargino and neutralino spectra and couplings are modified in a distinctive way. These operators can be generated by a variety of microscopic mechanisms.

Higgs physics as a window beyond the MSSM

As is well known, electroweak breaking in the MSSM requires substantial fine-tuning, mainly due to the smallness of the tree-level Higgs quartic coupling, λtree. Hence the fine tuning is efficiently reduced in supersymmetric models with larger λtree, as happens naturally when the breaking of SUSY occurs at a low scale (not far from the TeV). We show, in general and with specific examples, that a dramatic improvement of the fine tuning (so that there is virtually no fine-tuning) is indeed a very common feature of these scenarios for wide ranges of tanβ and the Higgs mass (which can be as large as several hundred GeV if desired, but this is not necessary). The supersymmetric flavour problems are also drastically improved due to the absence of RG cross-talk between soft mass parameters.

/pdf/the-mssm-fine-tuning-problem-a-way-out-k6ft4wratz.pdf

Irene Hidalgo

Papers

The MSSM fine tuning problem: a way out