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Register a new userDetecting a heavy neutrino electric dipole moment at the LHC
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The milliQan Collaboration has proposed to search for millicharged particles by looking for very weakly ionizing tracks in a detector installed in a cavern near the CMS experiment at the LHC. We note that another form of exotica can also yield weakly ionizing tracks. If a heavy neutrino has an electric dipole moment (EDM), then the milliQan experiment may be sensitive to it as well. In particular, writing the general dimension-5 operator for an EDM with a scale of a TeV and a one-loop factor, one finds a potential EDM as high as a few times $10^{-17}$ e-cm, and models exist where it is an order of magnitude higher. Redoing the Bethe calculation of ionization energy loss for an EDM, it is found that the milliQan detector is sensitive to EDMs as small as $10^{-17}$ e-cm. Using the production cross-section and analyzing the acceptance of the milliQan detector, we find the expected $95%$ exclusion and $3sigma$ sensitivity over the range of neutrino masses from $5-1000$ GeV for integrated luminosities of $300$ and $3000 {rm fb}^{-1}$ at the LHC.
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We investigate the prospects of the search for a nonzero $tau$ EDM form factor $d_tau(s)$ in $tau$ pair production by $e^+ e^-$ collisions at BEPC-II collider energies. We compute the expectation values and covariances of simple and optimal $CP$-odd observables for $tau$-pair production at $sqrt{s}=4.18$ GeV and $4.95$ GeV with subsequent decays of $tau^pm$ into major leptonic or semihadronic modes. For the $tau$ decays to two pions and three charged pions we take the full kinematic information of the hadronic system into account. Applying cuts and using realistic assumptions on the eventually attainable integrated luminosities at these energies, ${cal L}(4.18) = 3times 10^4~{rm pb}^{-1}$ and ${cal L}(4.95) = 10^4~{rm pb}^{-1}$, respectively, we find the following. By taking into account purely semihadronic and semihadronic-leptonic $tau^+tau^-$ decays one can achieve with optimal $CP$-odd observables the 1 s.d. sensitivities $delta {rm Re} d_tau = 4.5times 10^{-18}$ ecm ($5.3times 10^{-18}$ ecm) and $delta {rm Im} d_tau = 2.2 times 10^{-18}$ ecm ($2.7times 10^{-18}$ ecm) at $sqrt{s}=4.18$ GeV ($4.95$ GeV).
Permanent electric dipole moments (EDMs) of fundamental particles provide powerful probes for physics beyond the Standard Model. We propose to search for the EDM of strange and charm baryons at LHC, extending the ongoing experimental program on the neutron, muon, atoms, molecules and light nuclei. The EDM of strange Lambda baryons, selected from weak decays of charm baryons produced in pp collisions at LHC, can be determined by studying the spin precession in the magnetic field of the detector tracking system. A test of CPT symmetry can be performed by measuring the magnetic dipole moment of Lambda and anti-Lambda baryons. For short-lived Lambdac+ and Xic+ baryons, to be produced in a fixed-target experiment using the 7 TeV LHC beam and channeled in a bent crystal, the spin precession is induced by the intense electromagnetic field between crystal atomic planes. The experimental layout based on the LHCb detector and the expected sensitivities in the coming years are discussed.
We extract the neutron electric dipole moment $vert vec{d}_Nvert$ within the lattice QCD formalism. We analyse one ensemble of $N_f=2+1+1$ twisted mass clover-improved fermions with lattice spacing of $a simeq 0.08 {rm fm}$ and physical values of the quark masses corresponding to a pion mass $m_{pi} simeq 139 {rm MeV}$. The neutron electric dipole moment is extracted by computing the $CP$-odd electromagnetic form factor $F_3(Q^2 to 0)$ through small $theta$-expansion of the action. This approach requires the calculation of the topological charge for which we employ a fermionic definition by means of spectral projectors while we also provide a comparison with the gluonic definition accompanied by the gradient flow. We show that using the topological charge from spectral projectors leads to absolute errors that are more than two times smaller than those provided when the field theoretic definition is employed. We find a value of $vert vec{d}_Nvert = 0.0009(24) theta e cdot {rm fm}$ when using the fermionic definition, which is statistically consistent with zero.
In the context of supersymmetry, the two-loop Barr-Zee diagrams which induce CP-violating electric dipole moment of electron due to superpartners simultaneously yield CP-conserving magnetic dipole moment of muon. In this paper, we derive the coherence between the electric and magnetic dipole moments at two-loop level due to stops, charginos or neutralinos-charginos. We also use the coherence to constrain superpartner masses and their CP-violating phases, in the light of recent ACME limit on the electric dipole moment of electron and future experiments about magnetic dipole moment of muon such as Fermilab E989 experiment.
The connection between a regularization-independent symmetric momentum substraction (RI-$tilde{rm S}$MOM) and the $overline{rm MS}$ scheme for the quark chromo EDM operators is discussed. A method for evaluating the neutron EDM from quark chromoEDM is described. A preliminary study of the signal in the matrix element using clover quarks on a highly improved staggered quark (HISQ) ensemble is shown.
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