Naturalness upper bounds on gauge-mediated soft terms

Ciafaloni, Paolo; Струмиа, Алессандро

doi:10.1016/s0550-3213(97)00138-7

Cited by 88 publications

(120 citation statements)

References 30 publications

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“…This can be intuitively seen as follows. Expanding m 2 h (θ i ) around a point in the parameter space that gives the desired cancellation, say {θ 0 i }, up to first order in the parameters, one finds that only a small neighborhood δθ i ∼ θ 0 i /∆ θ i around this point gives a value of m 2 h smaller or equal to the experimental value [28]. Therefore, if one assumes that θ i could reasonably have taken any value of the order of magnitude of θ 0 i , then only for a small fraction δθ i /θ 0 i ∼ ∆ −1 θ i of this region one gets m 2 h < ∼ (m exp h ) 2 , hence the rough probabilistic meaning of ∆ θ i .…”

Section: The Measure Of the Fine-tuningmentioning

confidence: 97%

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What is a natural SUSY scenario?

Casas

Moreno

Robles

et al. 2015

J. High Energ. Phys.

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The idea of "Natural SUSY", understood as a supersymmetric scenario where the fine-tuning is as mild as possible, is a reasonable guide to explore supersymmetric phenomenology. In this paper, we re-examine this issue in the context of the MSSM including several improvements, such as the mixing of the fine-tuning conditions for different soft terms and the presence of potential extra fine-tunings that must be combined with the electroweak one. We give tables and plots that allow to easily evaluate the fine-tuning and the corresponding naturalness bounds for any theoretical model defined at any high-energy (HE) scale. Then, we analyze in detail the complete fine-tuning bounds for the unconstrained MSSM, defined at any HE scale. We show that Natural SUSY does not demand light stops. Actually, an average stop mass below 800 GeV is disfavored, though one of the stops might be very light. Regarding phenomenology, the most stringent upper bound from naturalness is the one on the gluino mass, which typically sets the present level fine-tuning at O(1%). However, this result presents a strong dependence on the HE scale. E.g. if the latter is 10 7 GeV the level of fine-tuning is ∼ four times less severe. Finally, the most robust result of Natural SUSY is by far that Higgsinos should be rather light, certainly below 700 GeV for a fine-tuning of O(1%) or milder. Incidentally, this upper bound is not far from 1 TeV, which is the value required if dark matter is made of Higgsinos.

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Section: The Measure Of the Fine-tuningmentioning

confidence: 97%

“…In ref. [28] it was argued that (the maximum of all) |∆ θ i | represents the inverse of the probability of a cancellation among terms of a given size to obtain a result which is |∆ θ i | times smaller. This can be intuitively seen as follows.…”

Section: The Measure Of the Fine-tuningmentioning

confidence: 99%

What is a natural SUSY scenario?

Casas

Moreno

Robles

et al. 2015

J. High Energ. Phys.

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“…Here we work in conventions in which v 246 GeV. 3 We use the modified definition of fine tuning for the top-Yukawa coupling, appropriate for measured parameters [33].…”

Section: The Fine Tuning Measurementioning

confidence: 99%

Non-universal gaugino masses and fine tuning implications for SUSY searches in the MSSM and the GNMSSM

Kaminska

Ross

Schmidt-Hoberg

2013

J. High Energ. Phys.

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For the case of the MSSM and the most general form of the NMSSM (GN-MSSM) we determine the reduction in the fine tuning that follows from allowing gaugino masses to be non-degenerate at the unification scale, taking account of the LHC8 bounds on SUSY masses, the Higgs mass bound, gauge coupling unification and the requirement of an acceptable dark matter density. We show that low-fine tuned points fall in the region of gaugino mass ratios predicted by specific unified and string models. For the case of the MSSM the minimum fine tuning is still large, approximately 1:60 allowing for a 3 GeV uncertainty in the Higgs mass (1:500 for the central value), but for the GNMSSM it is below 1:20. We find that the spectrum of SUSY states corresponding to the low-fine tuned points in the GNMSSM is often compressed, weakening the LHC bounds on coloured states. The prospect for testing the remaining low-fine-tuned regions at LHC14 is discussed.

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“…explicitly defined in [10]. In practice 2∆ reduces to d when ∆ ≫ 1 and is up to 30% lower than it in all cases of interest.…”

mentioning

confidence: 99%

“…Partly, this is where the ambiguity of the quantitative concept comes in. We stick to a definition [10] that avoids these criticisms by replacing the logarith- mic derivatives present in the original definition…”

mentioning

confidence: 99%

About the fine-tuning price of LEP

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Following Chankowski, Ellis and Pokorski we quantify the amount of fine-tuning of input parameters of the Minimal Supersymmetric Standard Model that is needed to respect the lower limits on sparticle and Higgs masses imposed by negative searches so far, direct or indirect. By including the one loop radiative corrections to the effective potential, the amount of fine-tuning is reduced with respect to the results of CEP by a factor of 2 ÷ 5, strongly increasing as tan β approaches 1. A further reduction factor may come from a more appropriate, less restrictive, definition of the fine-tuning parameter itself.Extensive searches of supersymmetric signals, done mostly, but not only, at LEP, explore in a significant way the parameter space of the Minimal Supersymmetric Standard Model (MSSM). Although variations on the MSSM are certainly possible, the MSSM is, in some of its aspects, representative enough to make these searches relevant in absolute terms, hence the importance of assessing their significance in a quantitative way. In essence, how much should one worry about the fact that no positive result has been found so far? Or, even more importantly, how critical are, to test the MSSM, the searches that will be performed in the nearest future?A first important attempt to answer these questions has been recently made by Chankowski, Ellis and Pokorski A way to summarise the results of CEP is the following:• An amount of fine tuning ∆ greater than about 20 is required for any value of tan β;• A scalar Higgs lighter than 90 GeV, that will be searched for at LEP in the near future, requires ∆ > ∼ 60;• A value of tan β lower than 2, a range suggested by an infra-red fixed-point analysis, requires ∆ greater than about 100.Since ∆ is supposed to measure, although in a rough way, the inverse probability of an unnatural cancellation to occur in the expression that relates the Zboson mass to the various MSSM parameters, the results of CEP are striking enough to suggest that we take a closer look at them, which is what we do in this letter. This is without underestimating the difficulty of giving an unambiguous quantitative meaning to the 'naturalness bounds' on the sparticle masses, as correctly emphasised by CEP themselves. Our results are summarised in fig. 1, which gives the prize of the fine tuning ∆ as a scatter plot in the MSSM parameters space still consistent with the data mentioned above and considered by CEP * . As seen from fig. 1, we have a lower limit on ∆ which is about a factor of 5 ÷ 10 weaker than that obtained * The density of points in this plot does not have any particular meaning. What counts is rather the enveloping curve at the lower bound of the populated region.

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Naturalness upper bounds on gauge-mediated soft terms

Cited by 88 publications

References 30 publications

What is a natural SUSY scenario?

What is a natural SUSY scenario?

Non-universal gaugino masses and fine tuning implications for SUSY searches in the MSSM and the GNMSSM

About the fine-tuning price of LEP

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