QCD factorization of the four-lepton decay $$B^-\rightarrow \ell \bar{\nu }_\ell \ell ^{(\prime )} \bar{\ell }^{(\prime )}$$

Motivated by the first search for the rare charged-current B decay to four leptons, $$\ell \bar{\nu }_\ell \ell ^{(\prime )} \bar{\ell }^{(\prime )}$$ ℓ ν ¯ ℓ ℓ ( ′ ) ℓ ¯ ( ′ ) , we calculate the decay amplitude with factorization methods. We obtain the $$B\rightarrow \gamma ^*$$ B → γ ∗ form factors, which depend on the invariant masses of the two lepton pairs, at leading power in an expansion in $$\Lambda _\mathrm{QCD}/m_b$$ Λ QCD / m b to next-to-leading order in $$\alpha _s$$ α s , and at $$\mathcal {O}(\alpha _s^0)$$ O ( α s 0 ) at next-to-leading power. Our calculations predict branching fractions of a few times $$10^{-8}$$ 10 - 8 in the $$\ell ^{(\prime )} \bar{\ell }^{(\prime )}$$ ℓ ( ′ ) ℓ ¯ ( ′ ) mass-squared bin up to $$q^2=1~$$ q 2 = 1 GeV$$^2$$ 2 with $$n_+q>3~$$ n + q > 3 GeV. The branching fraction rapidly drops with increasing $$q^2$$ q 2 . An important further motivation for this investigation has been to explore the sensitivity of the decay rate to the inverse moment $$\lambda _B$$ λ B of the leading-twist B meson light-cone distribution amplitude. We find that in the small-$$q^2$$ q 2 bin, the sensitivity to $$\lambda _B$$ λ B is almost comparable to $$B^- \rightarrow \mathrm {\ell }^- \bar{\nu }_{\mathrm {\ell }}\gamma $$ B - → ℓ - ν ¯ ℓ γ when $$\lambda _B$$ λ B is small, but with an added uncertainty from the light-meson intermediate resonance contribution. The sensitivity degrades with larger $$q^2$$ q 2 .

Statistical Behavior of Lepton Pair Spectrum in the Drell-Yan Process and Signal from Quark-Gluon Plasma in High-Energy Collisions

We analyze the transverse momentum ( p T ) spectra of lepton pairs ( ℓ ℓ ¯ ) generated in the Drell-Yan process, as detected in proton-nucleus (pion-nucleus) and proton-(anti)proton collisions by ten collaborations over a center-of-mass energy s N N or s if in a simplified form) range from ~ 20 GeV to above 10 TeV. Three types of probability density functions (the convolution of two Lévy-Tsallis functions, the two-component Erlang distribution, and the convolution of two Hagedorn functions) are utilized to fit and analyze the p T spectra. The fit results are approximately in agreement with the collected experimental data. Consecutively, we obtained the variation law of related parameters as a function of s and invariant mass Q . In the fit procedure, a given Lévy-Tsallis (or Hagedorn) function can be regarded as the probability density function of transverse momenta contributed by a single quark ( q ) or anti-quark ( q ¯ ). The Drell-Yan process is then described by the statistical method.

Measurement of the transverse momentum distribution of Drell–Yan lepton pairs in proton–proton collisions at $$\sqrt{s}=13\,$$TeV with the ATLAS detector

This paper describes precision measurements of the transverse momentum $$p_\mathrm {T}^{\ell \ell }$$pTℓℓ ($$\ell =e,\mu $$ℓ=e,μ) and of the angular variable $$\phi ^{*}_{\eta }$$ϕη∗ distributions of Drell–Yan lepton pairs in a mass range of 66–116 GeV. The analysis uses data from 36.1 fb$$^{-1}$$-1 of proton–proton collisions at a centre-of-mass energy of $$\sqrt{s}=13\,$$s=13TeV collected by the ATLAS experiment at the LHC in 2015 and 2016. Measurements in electron-pair and muon-pair final states are performed in the same fiducial volumes, corrected for detector effects, and combined. Compared to previous measurements in proton–proton collisions at $$\sqrt{s}=7$$s=7 and $$8\,$$8TeV, these new measurements probe perturbative QCD at a higher centre-of-mass energy with a different composition of initial states. They reach a precision of 0.2$$\%$$% for the normalized spectra at low values of $$p_\mathrm {T}^{\ell \ell }$$pTℓℓ. The data are compared with different QCD predictions, where it is found that predictions based on resummation approaches can describe the full spectrum within uncertainties.

Sensitivity on anomalous neutral triple gauge couplings via ZZ production at FCC-hh

We study the sensitivity of anomalous neutral triple gauge couplings (aNTGC) via $$pp \rightarrow ZZ$$pp→ZZ production in the 4$$\ell $$ℓ channel at 100 TeV center of mass energy of future circular hadron collider, . The analysis including the realistic detector effects is performed in the mode where both Z bosons decay into same-flavor, oppositely charged lepton pairs. The sensitivities to the charge–parity (CP)-conserving couplings $$C_{{\tilde{B}}W} / \Lambda ^{4}$$CB~W/Λ4 and CP-violating couplings $$C_{WW} / \Lambda ^{4}$$CWW/Λ4, $$C_{BW} / \Lambda ^{4}$$CBW/Λ4 and $$C_{BB} / \Lambda ^{4}$$CBB/Λ4 obtained at 95% Confidence Level using the invariant mass distribution of the 4$$\ell $$ℓ system reconstructing the leading and sub-leading Z boson candidates are $$[-\,0.09, \,\, +\,0.09]$$[-0.09,+0.09], $$[-\,0.21, \,\, +\,0.21]$$[-0.21,+0.21], $$[-\,0.26, \,\, +\,0.26]$$[-0.26,+0.26], and $$[-\,0.10, \,\, +\,0.10]$$[-0.10,+0.10] in units of $$\hbox {TeV}^{-4}$$TeV-4, respectively.

Effect of nuclear magnetic distribution on thephoto production of longitudinally polarizedlepton-pairs in the field of Na2311 and Al2713 nuclei

In this work we treat the influence of the nuclear magnetic moment on the photo production of e - e+, ?- ?+, ?- ?+ i. e. l- l+, lepton pairs. We examine the process: ? + N(Ze, ?j ) ? N(Ze, ?j ) + l-(p- ) + l+(p+) of production of (l- l+) - pairs by cir?cularly polarized photons ?(p?) in the field of nucleus, N, having electric (coulomb) charge Ze, and magnetic dipole moment ?j, where j is the nuclear spin. Taking into account the longitudinal polarizations of the produced pairs, we calculate the differential cross-sections for the angular and energy distributions of the pair particles. We investigate the effect of the nuclear magnetic moment on the angular and energy distribution of the antilepton l+(e+,?+,?+), showing that the contribution the cross-section from the nuclear magnetic dipole moment rises considerably on going to high energies of incident photon and large emission angles of the pair particles. The results of calculations for Na2311 (j =1/2) and Al2713 - target nuclei, and for the three lepton pair types (e - e+, ?- ?+, ?- ?+) are presented graphically [1, 2].

Effect of nuclear magnetic distribution on thephoto production of longitudinally polarizedlepton-pairs in the field of Na2311 and Al2713 nuclei

In this work we treat the influence of the nuclear magnetic moment on the photo production of e - e+, ?- ?+, ?- ?+ i. e. l- l+, lepton pairs. We examine the process: ? + N(Ze, ?j ) ? N(Ze, ?j ) + l-(p- ) + l+(p+) of production of (l- l+) - pairs by cir?cularly polarized photons ?(p?) in the field of nucleus, N, having electric (coulomb) charge Ze, and magnetic dipole moment ?j, where j is the nuclear spin. Taking into account the longitudinal polarizations of the produced pairs, we calculate the differential cross-sections for the angular and energy distributions of the pair particles. We investigate the effect of the nuclear magnetic moment on the angular and energy distribution of the antilepton l+(e+,?+,?+), showing that the contribution the cross-section from the nuclear magnetic dipole moment rises considerably on going to high energies of incident photon and large emission angles of the pair particles. The results of calculations for Na2311 (j =1/2) and Al2713 - target nuclei, and for the three lepton pair types (e - e+, ?- ?+, ?- ?+) are presented graphically [1, 2].