The Selfish Higgs Giudice, G.F.; Kehagias, A.; Riotto, A.
The journal of high energy physics,
10/2019, Letnik:
2019, Številka:
10
Journal Article
Recenzirano
Odprti dostop
A
bstract
We propose a mechanism to solve the Higgs naturalness problem through a cosmological selection process. The discharging of excited field configurations through membrane nucleation leads to ...discrete jumps of the cosmological constant and the Higgs mass, which vary in a correlated way. The resulting multitude of universes are all empty, except for those in which the cosmological constant and the Higgs mass are both nearly vanishing. Only under these critical conditions can inflation be activated and create a non-empty universe.
Testing new physics with the electron g − 2 Giudice, G. F.; Paradisi, P.; Passera, M.
The journal of high energy physics,
11/2012, Letnik:
2012, Številka:
11
Journal Article
Recenzirano
Odprti dostop
A
bstract
We argue that the anomalous magnetic moment of the electron (
a
e
) can be used to probe new physics. We show that the present bound on new-physics contributions to
a
e
is 8 × 10
−13
, but ...the sensitivity can be improved by about an order of magnitude with new measurements of
a
e
and more refined determinations of
α
in atomic-physics experiments. Tests on new-physics effects in
a
e
can play a crucial role in the interpretation of the observed discrepancy in the anomalous magnetic moment of the muon (
a
μ
). In a large class of models, new contributions to magnetic moments scale with the square of lepton masses and thus the anomaly in
a
μ
suggests a new-physics effect in
a
e
of (0
.
7 ± 0
.
2) × 10
−13
. We also present examples of new-physics theories in which this scaling is violated and larger effects in
a
e
are expected. In such models the value of
a
e
is correlated with specific predictions for processes with violation of lepton number or lepton universality, and with the electric dipole moment of the electron.
Extrapolating the Standard Model to high scales using the renormalisation group, three possibilities arise, depending on the mass of the Higgs boson: if the Higgs mass is large enough the Higgs ...self-coupling may blow up, entailing some new non-perturbative dynamics; if the Higgs mass is small the effective potential of the Standard Model may reveal an instability; or the Standard Model may survive all the way to the Planck scale for an intermediate range of Higgs masses. This latter case does not necessarily require stability at all times, but includes the possibility of a metastable vacuum which has not yet decayed. We evaluate the relative likelihoods of these possibilities, on the basis of a global fit to the Standard Model made using the Gfitter package. This uses the information about the Higgs mass available directly from Higgs searches at LEP and now the Tevatron, and indirectly from precision electroweak data. We find that the ‘blow-up’ scenario is disfavoured at the 99% confidence level (96% without the Tevatron exclusion), whereas the ‘survival’ and possible ‘metastable’ scenarios remain plausible. A future measurement of the mass of the Higgs boson could reveal the fate of the Standard Model.
The naturalness criterion applied to the cosmological constant implies a new-physics threshold at
10
−
3
eV
. Either the naturalness criterion fails, or this threshold does not influence particle ...dynamics at higher energies. It has been suggested that the Higgs naturalness problem may follow the same fate. We investigate this possibility and, abandoning the hierarchy problem, we use unification and dark matter as the only guiding principles. The model recently proposed by Arkani-Hamed and Dimopoulos emerges as a very interesting option. We study it in detail, analysing its structure, and the conditions for obtaining unification and dark matter.
The dark-matter prediction is usually considered as one of the successes of low-energy supersymmetry. We argue that, after LEP constraints are taken into account, the correct prediction for the ...dark-matter density, at a quantitative level, is no longer a natural consequence of supersymmetry, but it requires special relations among parameters, highly sensitive to small variations. This is analogous to the problem of electroweak-symmetry breaking, where the correct value of the
Z mass is obtained only with a certain degree of fine tuning. In the general parameter space of low-energy supersymmetry, one of the most plausible solution to reproduce the correct value of the dark-matter density is the well-tempered neutralino, which corresponds to the boundary between a pure bino and a pure higgsino or wino. We study the properties of well-tempered neutralinos and we propose a simple limit of split supersymmetry that realizes this situation.
We explore some fundamental differences in the phenomenology, cosmology and model building of Split Supersymmetry compared with traditional low-scale supersymmetry. We show how the mass spectrum of ...Split Supersymmetry naturally emerges from theories where the dominant source of supersymmetry breaking preserves an
R symmetry, characterize the class of theories where the unavoidable
R-breaking by gravity can be neglected, and point out a new possibility, where supersymmetry breaking is directly communicated at tree level to the visible sector via renormalizable interactions. Next, we discuss possible low-energy signals for Split Supersymmetry. The absence of new light scalars removes all the phenomenological difficulties of low-energy supersymmetry, associated with one-loop flavor and CP-violating effects. However, the electric dipole moments of leptons and quarks do arise at two loops, and are automatically at the level of present limits with no need for small phases, making them accessible to several ongoing new-generation experiments. We also study proton decay in the context of Split Supersymmetry, and point out scenarios where the dimension-six induced decays may be observable. Finally, we show that the novel spectrum of Split Supersymmetry opens up new possibilities for the generation of dark matter, as the decays of ultraheavy gravitinos in the early universe typically increase the abundance of the lightest neutralino above its usual freeze-out value. This allows for lighter gauginos and Higgsinos, more accessible both to the LHC and to dark-matter detection experiments.
We present a general analysis of extensions of the Standard Model which satisfy the criterion of Minimal Flavour Violation (MFV). We define this general framework by constructing a low-energy ...effective theory containing the Standard Model fields, with one or two Higgs doublets and, as the only source of SU(3)
5 flavour symmetry breaking, the background values of fields transforming under the flavour group as the ordinary Yukawa couplings. We analyse present bounds on the effective scale of dimension-six operators, which range between 1 and 10 TeV, with the most stringent constraints imposed by
B→
X
s
γ. In this class of theories, it is possible to relate predictions for FCNC processes in
B physics to those in
K physics. We compare the sensitivity of various experimental searches in probing the hypothesis of MFV. Within the two-Higgs-doublet scenario, we develop a general procedure to obtain all tan
β-enhanced Higgs-mediated FCNC amplitudes, discussing in particular their impact in
B→ℓ
+ℓ
−,
ΔM
B
and
B→
X
s
γ. As a byproduct, we derive some two-loop tan
β-enhanced supersymmetric contributions to
B→
X
s
γ previously unknown.
This study is aimed to analyze the clinical outcome of recurrent ovarian cancer patients bearing isolated lymph-node recurrence (ILNR) who underwent salvage lymphadenectomy (SL). The prognostic role ...of clinicopathological variables and the mutational status of BRCA1/2 have also been investigated.
This retrospective, single-institutional study included women with platinum-sensitive lymph node recurrence underwent to SL between June 2008 and June 2018. Univariate and multivariate analysis was performed to evaluate the impact of clinical parameters, and BRCA1/2 mutational status on post salvage lymphadenectomy progression-free survival (PSL-PFS).
As of June 2019, the median follow-up after SL was 30 months, and the relapse has been documented in 48 (56.5%) patients. In the whole series, the median PSL-PFS was 21 months, and the 3-year PSL-PFS was 36.7%. The median PSL-PFS, according to patients with ILNR (N = 71) versus patients with lymph-nodes and other sites of disease (N = 14), was 27 months versus 12 months, respectively.
Univariate analysis of variables conditioning PSL-PFS showed that platinum-free interval (PFI) ≥12 months, normal Ca125 serum levels, and number of metastatic lymph-nodes ≤3 played a statistically significant favorable role. In multivariate analysis, PFI duration ≥12 months and the number of metastatic lymph nodes ≤3 were shown to keep their favorable, independent prognostic value on PSL-PFS.
In the context of SL, the patients with long PFI and low metastatic lymph node numbers at ILNR diagnosis have the best outcome. The BRCA mutational status seems not associated with clinical variables and PSL-PFS, differently from other sites of disease in ROC patients.
The detection of primordial gravitational waves would not only have extraordinary implications for our understanding of early cosmology, but would also give non-trivial constraints on Standard Model ...parameters, under the assumption that no new physics enters below the Higgs instability scale. We study the resulting bounds on the top quark mass and the strong coupling constant, discussing their theoretical uncertainties and their robustness against changes in other parameters.
Theories with gauge-mediated supersymmetry breaking provide an interesting alternative to the scenario in which the soft terms of the low-energy fields are induced by gravity. These theories allow ...for a natural suppression of flavour violations in the supersymmetric sector and have very distinctive phenomenological features. Here we review their basic structure, their experimental implications, and the attempts to embed them into models in which all mass scales are dynamically generated from a single fundamental scale.
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