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Register a new userLong range forces and limits on unparticle interactions
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Couplings between standard model particles and unparticles from a nontrivial scale invariant sector can lead to long range forces. If the forces couple to quantities such as baryon or lepton (electron) number, stringent limits result from tests of the gravitational inverse square law. These limits are much stronger than from collider phenomenology and astrophysics.
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Unparticles as suggested by Georgi are identities that are not constrained by dispersion relations but are governed by their scaling dimension, d. Their coupling to particles can result in macroscopic interactions between matter, that are generally an inverse nonintegral power of distance. This is totally different from known macroscopic forces. We use the precisely measured long-ranged spin-spin interaction of electrons to constrain unparticle couplings to the electron. For 1<d<1.5 the axial vector unparticle coupling is excluded; and for 1<d<1.3 the pseudoscalar and vector couplings are also ruled out. These bounds and the ones for other ranges of d exceed or are complementary to those obtained previously from exotic positronium decays.
We show that a previous polarized 3He experiment at Princeton, plus Eot-Wash equivalence-principle tests, constrain exotic, long-ranged (lambda > 0.15m) parity-violating interactions of neutrons at levels well below those inferred from a recent study of the parity-violating spin-precession of neutrons transmitted through liquid 4He. For lambda > 1.0e8 meters the bounds on gAgV are improved by a 11 orders of magnitude.
We quantify the effect of gauge bosons from a weakly coupled lepton flavor dependent $U(1)$ interaction on the matter background in the evolution of solar, atmospheric, reactor and long-baseline accelerator neutrinos in the global analysis of oscillation data. The analysis is performed for interaction lengths ranging from the Sun-Earth distance to effective contact neutrino interactions. We survey $sim 10000$ set of models characterized by the six relevant fermion $U(1)$ charges and find that in all cases, constraints on the coupling and mass of the $Z$ can be derived. We also find that about 5% of the $U(1)$ model charges lead to a viable LMA-D solution but this is only possible in the contact interaction limit. We explicitly quantify the constraints for a variety of models including $U(1)_{B-3L_e}$, $U(1)_{B-3L_mu}$, $U(1)_{B-3L_tau}$, $U(1)_{B-frac{3}{2}(L_mu+L_tau)}$, $U(1)_{L_e-L_mu}$, $U(1)_{L_e-L_tau}$, $U(1)_{L_e-frac{1}{2}(L_mu+L_tau)}$. We compare the constraints imposed by our oscillation analysis with the strongest bounds from fifth force searches, violation of equivalence principle as well as bounds from scattering experiments and white dwarf cooling. Our results show that generically, the oscillation analysis improves over the existing bounds from gravity tests for $Z$ lighter than $sim 10^{-8} to 10^{-11}$ eV depending on the specific couplings. In the contact interaction limit, we find that for most models listed above there are values of $g$ and $M_{Z}$ for which the oscillation analysis provides constraints beyond those imposed by laboratory experiments. Finally we illustrate the range of $Z$ and couplings leading to a viable LMA-D solution for two sets of models.
We study unparticle effects on particle and antiparticle osillations in meson-antimeson, and muonium-antimuonium systems. Unlike usual tree level contributions to meson oscillations from heavy particle exchange with small $Gamma_{12}$, the unparticle may have sizeable contributions to both $M_{12}$ and $Gamma_{12}$ due to fractional dimension $d_U$ of the unparticle. We find that very stringent constraints on the unparticle and particle interactions can be obtained. If unparticle effect dominates the contributions (which may happen in $D^0-bar D^0$ mixing) to meson mixing parameters $x$ and $y$, we find that $x/y =cot(pi d_U)$. Interesting constraints on unparticle and particle interactions can also be obtained using muonion and antimuonion oscillation data. We also comment on unparticle effects on CP violation in meson oscillations.
The hadronic form factors of the energy-momentum tensor (EMT) have attracted considerable interest in recent literature. This concerns especially the D-term form factor D(t) with its appealing interpretation in terms of internal forces. With their focus on hadron structure, theoretical studies so far have concentrated on strongly interacting systems with short-range forces. Effects on the EMT due to long-range forces like the electromagnetic interaction have not yet been studied. Electromagnetic forces play a small role in the balance of forces inside the proton, but their long-range nature introduces new features which are not present in systems with short-range forces. We use a simple but consistent classical field theoretical model of the proton to show how the presence of long-range forces alters some notions taken for granted in short-range systems. Our results imply that a more careful definition of the D-term is required when long-range forces are present.
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