Cosmic rays, antihelium, and an old navy spotlight

Abstract

Cosmic-ray anti-deuterium and anti-helium have long been suggested as probes of dark matter, as their secondary astrophysical production was thought extremely scarce. But how does one actually predict the secondary flux? Anti-nuclei are dominantly produced in pp collisions, where laboratory cross section data is lacking. We make a new attempt at tackling this problem by appealing to a scaling law of nuclear coalescence with the physical volume of the hadronic emission region. The same volume is probed by Hanbury Brown-Twiss (HBT) two-particle correlations. We demonstrate the consistency of the scaling law with systems ranging from central and off-axis AA collisions to pA collisions, spanning 3 orders of magnitude in coalescence yield. Extending the volume scaling to the pp system, HBT data allows us to make a new estimate of coalescence, that we test against preliminary ALICE pp data. For anti-helium the resulting cross section is 1-2 orders of magnitude higher than most earlier estimates. The astrophysical secondary flux of anti-helium could be within reach of a five-year exposure of AMS02.challenge, instead, is in computing the production cross sections. Invoking the HBT-coalescence relation, we derive new estimates for thed and 3 He yield in pp collisions, forming the basis of our results in Fig.

Longitudinal short-distance constraints for the hadronic light-by-light contribution to (g − 2)μ with large-Nc Regge models

“…(C. 28) i.e., the error we make by keeping only the leading term in the expansion of the ψ (1) in (C.19) is subdominant. When considering the high-energy region Q 2 1 ≈ Q 2 2 ≈ Q 2 3 = Q 2 , the same technique can be applied, but the situation simplifies slightly, since there is only one large scale.…”

“…Since the HVP contribution can be systematically calculated with a data-driven dispersive approach [5-9], lattice QCD [10][11][12][13][14][15][16], and potentially be accessed independently by the proposed MUonE experiment [17,18], which aims to measure the space-like finestructure constant α(t) in elastic electron-muon scattering, the HLbL contribution may end up dominating the theoretical error. 1 Apart from lattice QCD [27][28][29], recent data-driven approaches towards HLbL scattering are again rooted in dispersion theory, either for the HLbL tensor [30][31][32][33][34][35], the Pauli 1 Note that higher-order insertions of HVP [5,19,20] and HLbL [21] are already under sufficient control, as are hadronic corrections in the anomalous magnetic moment of the electron, where recently a 2.5 σ tension between the direct measurement [22] and the SM prediction [23] using the fine-structure constant from Cs interferometry [24] emerged [25,26].…”

Combined explanations of (g−2)μ,e and implications for a large muon EDM

“…The experimental value of the muon g − 2 [1] a exp µ = 116,592,089(63) × 10 −11 (1) differs from the SM prediction at the level of 3-4σ, for definiteness we take [2] ∆a µ = a exp µ − a SM µ ∼ 270(85) × 10 −11 (2) as an estimate of the current status. Recent advances in corroborating and improving the SM prediction include hadronic vacuum polarization [3][4][5][6][7][8][9][10], hadronic light-by-light scattering [11][12][13][14][15][16][17][18][19], and higher-order hadronic corrections [20,21]. The release of first results from the Fermilab experiment [22] is highly anticipated, while a complementary strategy based on ultracold muons is being pursued at J-PARC [23], see also Ref.…”

Testing Production Scenarios for (Anti-)(Hyper-)nuclei with Multiplicity-dependent Measurements at the LHC

“…2 takes explicitly into account the source size (R), as the coalescence probability naturally decreases for nucleons with similar momenta that are produced far apart in configuration space. Moreover, the source size is identified with the effective sub-volume of the whole system that is governed by the (momentum-dependent) homogeneity length of the interacting nucleons and experimentally accessible with Hanbury-Brown-Twiss (HBT) interferometry [3,4]. Figure 1 shows the source radius dependence of B A for nuclei and hyper-nuclei with A = 2, 3 and 4 whose properties are reported in Tab.…”