(Who is afraid of) the actual silence of these zetta/zepto-spaces (?)

after the SM Higgs discovery by ATLAS, CMS and then CDF and D0

The ATLAS and CMS Collaborations recently reported strong evidence for Higgs boson decays to fermions [25–30], with sensitivity dominated by the H → τ +τ − decay mode, though they have not yet performed spin and parity tests using fermionic decays. The particle decaying fermionically for which the Tevatron also found evidence might not be the same as the particle discovered through its bosonic decays at the LHC. Tests of the spin and parity [23] with Tevatron data therefore provide unique information on the identity and properties of the new particle or particles. The CDF and D0 Collaborations have re-optimized their SM Higgs boson searches to test the exotic Higgs boson models in the WH → ℓνb¯b [31, 32], ZH → ℓ +ℓ −b ¯b [33, 34], and WH + ZH → E/T b ¯b [35, 36] channels, where ℓ = e or µ and E/T is the missing transverse energy [37]... 

...we combine CDF’s and D0’s tests for the presence of a pseudoscalar Higgs boson with J P = 0− and a graviton-like boson with J P = 2+ in the WX → ℓνb¯b, the ZX → ℓ +ℓ −b ¯b, and the VX → E/T b ¯b search channels using models described in Ref. [23]. The masses of the exotic bosons are assumed to be 125 GeV/c 2 . No evidence is seen for either exotic particle, either in place of the SM Higgs boson or produced in a mixture with a J P = 0+ Higgs boson. In both searches, the best-fit cross section times the decay branching ratio into a bottom-antibottom quark pair of a J P = 0+ signal component is consistent with the prediction of the SM Higgs boson.

Tevatron Constraints on Models of the Higgs Boson with Exotic Spin and Parity Using Decays to Bottom-Antibottom Quark Pairs

The CDF, D0 Collaborations

(Submitted on 3 Feb 2015 (v1), last revised 24 Mar 2015 (this version, v2))

... and the last measurement of the astrophysical antiproton to proton ratio by Ams-02

Since decades, the antiproton component in cosmic rays has been recognized as an important messenger for energetic phenomena of astrophysical, cosmological and particle physics nature (see for instance [1, 2, 3]). In modern times, antiprotons have often been argued to be an important diagnostic tool for cosmic ray sources and propagation properties, and constitute one of the prime channels for indirect searches of Dark Matter (DM) [4, 5], which so far has only been detected gravitationally. In DM annihilation (or decay) modes, antiprotons can result either from the hadronization of the primary quarks or gauge bosons or through electroweak radiation for leptonic channels. The Alpha Magnetic Spectrometer (Ams-02) onboard the International Space Station (ISS), is the most advanced detector for such indirect DM searches via charged cosmic ray flux measurements. The positron fraction has been published earlier [6, 7], confirming the rise at energies above 10 GeV detected previously by Pamela [8, 9] and Fermi [10]. The sum of electrons and positrons [11] as well as they separate fluxes [12] have also been published, thus drawing a coherent and extremely precise picture of the lepton components of cosmic rays. Despite the fact that DM interpretations of the positron and, more generally, leptonic ‘excesses’ have been attempted (for a review see [13]), even before the advent of Ams-02 it had been recognized that explanations involving astrophysical sources were both viable and favoured (for a review see [14]), a conclusion reinforced by updated analyses (see [15, 16], and references therein, for recent assessments).  

In this paper, we will instead focus on cosmic ray antiprotons. Up to now, the so-called secondary antiprotons (originating from collisions of cosmic ray primaries with the interstellar material) have been shown to account for the bulk of the measured flux [17], thus allowing to derive constraints on the DM parameter space and to compute expected sensitivities, respectively based on updated Pamela data [18] and projected Ams-02 data (see e.g. [19, 20, 21, 22, 23, 24]). Now that the Ams-02 Collaboration has presented its preliminary measurements of the ¯p/p ratio [25], with an improved statistical precision and energy range extending to 450 GeV, it is crucial and timely to re-examine the situation and update previous recent results. 

... 

In the light of the preliminary results recently presented by Ams-02 on proton and helium fluxes, as well as the antiproton to proton ratio, we have re-evaluated the secondary astrophysical predictions for the antiproton to proton ratio, accounting for the different sources of uncertainties: namely on the injection fluxes, on the production cross sections, on the propagation process and those connected to solar modulation. Our first and main result is that there is no unambiguous antiproton excess that can be identified in the first place, and thus, at this stage, no real need for primary sources of antiprotons. Within errors, secondary astrophysical production alone can account for the data.

AMS-02 antiprotons, at last! Secondary astrophysical component and immediate implications for Dark Matter

Gaëlle Giesen, Mathieu Boudaud, Yoann Genolini, Vivian Poulin, Marco Cirelli, Pierre Salati, Pasquale D. Serpico, Jie Feng, Antje Putze, Sylvie Rosier-Lees, Manuela Vecchi

(Submitted on 16 Apr 2015)

Poursuivant dans la veine du précédent billet (paraphrasant le même auteur), ce billet ci se voulait une illustration de ce que la physique expérimentale/phénoménologique se nourrit des données empiriques/contraintes qui s'imposent à elle pour lui éviter de délirer et de s'asservir à des ombres... 

Puisqu'il est toujours bon d'expliciter ses sources d'inspiration, notons que la notion de zepto-espace qui fait référence à l'échelle caractéristique sondée par le LHC a été magnifiquement popularisée par Gian Francesco Giudice. Quant-à l'odyssée du zetta-espace, elle n'a pas encore été écrite à ma connaissance mais c'est pourtant celle que nous raconte les rayons cosmiques collectés sur Terre et qui ont traversé la Voie Lactée dont la dimension caractéristique est, heureux hasard, de l'ordre du zettamètre ...

La lectrice/le lecteur du jour aura aussi noté ce matin le clin d'oeil à une pensée de Blaise Pascal.