Measurement of lepton momentum moments in the decayB ¯ → X l ν ¯
A. H. MahmoodS. E. CsornaI. DankóG. BonviciniD. CinabroM. DubrovinS. McGeeA. BornheimE. LipelesS. P. PappasA. ShapiroW. SunA. J. WeinsteinR. A. BriereG. P. ChenT. FergusonG. TatishviliH. VogelN. E. AdamJ. AlexanderK. BerkelmanV. BoisvertD. G. CasselP. S. DrellJ. E. DuboscqK. M. EcklundR. EhrlichR. S. GalikL. GibbonsB. GittelmanS. W. GrayD. L. HartillB. K. HeltsleyL. HsuC. D. JonesJ. KandaswamyD. L. KreinickA. MagerkurthH. Mahlke-KrügerT. O. MeyerN. B. MistryJ. R. PattersonD. PetersonJ. PivarskiS. J. RichichiD. RileyA. J. SadoffH. SchwarthoffM. R. ShepherdJ. G. ThayerD. UrnerT. WilksenA. WarburtonM. WeinbergerS. B. AtharP. AveryL. Breva-NewellV. PotliaH. StoeckJ. YeltonK. BenslamaB. I. EisensteinG. D. GollinI. KarlinerN. LowreyC. PlagerC. SedlackM. SelenJ. J. ThalerJ. S. WilliamsK. W. EdwardsR. AmmarD. BessonX. ZhaoS. AndersonV. FrolovD. T. GongY. KubotaS. Z. LiR. PolingA. SmithC. J. StepaniakJ. UrheimZ. MetreveliK. K. SethA. TomaradzeP. ZweberS. AhmedM. S. AlamJ. ErnstL. JianM. SaleemF. WapplerK. ArmsE. EckhartK. K. GanC. GwonK. HonscheidD. HufnagelH. KaganR. KassT. K. PedlarE. von ToerneM. M. ZoellerH. SeveriniP. SkubicS. A. DytmanJ. MuellerS. NamV. SavinovS. ChenJ. W. HinsonJ. LeeD. H. MillerV. PavluninE. I. ShibataI. P. J. ShipseyD. Cronin-HennessyA. L. LyonC. S. ParkW. ParkJ. B. ThayerE. H. ThorndikeT. E. CoanY. S. GaoF. LiuY. MaravinR. StroynowskiM. ArtusoC. BoulahouacheS. BluskK. BukinE. DambasurenR. MountainH. MuramatsuR. NandakumarT. SkwarnickiS. StoneJ. C. Wang
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Abstract:
We measure the primary lepton momentum spectrum in $\overline{B}\ensuremath{\rightarrow}X\mathcal{l}\overline{\ensuremath{\nu}}$ decays, for ${p}_{\mathcal{l}}>~1.5\mathrm{GeV}/c$ in the B rest frame. From this, we calculate various moments of the spectrum. In particular, we find ${R}_{0}\ensuremath{\equiv}{\ensuremath{\int}}_{1.7\mathrm{GeV}}(d\ensuremath{\Gamma}{/dE}_{\mathrm{sl}}{)dE}_{\mathcal{l}}/{\ensuremath{\int}}_{1.5\mathrm{GeV}}(d\ensuremath{\Gamma}{/dE}_{\mathrm{sl}}{)dE}_{\mathcal{l}}=0.6187\ifmmode\pm\else\textpm\fi{}{0.0014}_{\mathrm{stat}}\ifmmode\pm\else\textpm\fi{}{0.0016}_{\mathrm{sys}}$ and ${R}_{1}\ensuremath{\equiv}{\ensuremath{\int}}_{1.5\mathrm{GeV}}{E}_{\mathcal{l}}(d\ensuremath{\Gamma}{/dE}_{\mathrm{sl}}{)dE}_{\mathcal{l}}/{\ensuremath{\int}}_{1.5\mathrm{GeV}}(d\ensuremath{\Gamma}{/dE}_{\mathrm{sl}}{)dE}_{\mathcal{l}}=(1.7810\ifmmode\pm\else\textpm\fi{}{0.0007}_{\mathrm{stat}}\ifmmode\pm\else\textpm\fi{}{0.0009}_{\mathrm{sys}})\mathrm{GeV}.$ We use these moments to determine non-perturbative parameters governing the semileptonic width. In particular, we extract the heavy quark expansion parameters $\overline{\ensuremath{\Lambda}}=(0.39\ifmmode\pm\else\textpm\fi{}{0.03}_{\mathrm{stat}}\ifmmode\pm\else\textpm\fi{}{0.06}_{\mathrm{sys}}\ifmmode\pm\else\textpm\fi{}{0.12}_{\mathrm{th}})\mathrm{GeV}$ and ${\ensuremath{\lambda}}_{1}=(\ensuremath{-}0.25\ifmmode\pm\else\textpm\fi{}{0.02}_{\mathrm{stat}}\ifmmode\pm\else\textpm\fi{}{0.05}_{\mathrm{sys}}\ifmmode\pm\else\textpm\fi{}{0.14}_{\mathrm{th}}){\mathrm{GeV}}^{2}.$ The theoretical constraints used are evaluated through order ${1/M}_{B}^{3}$ in the non-perturbative expansion and ${\ensuremath{\beta}}_{0}{\ensuremath{\alpha}}_{s}^{2}$ in the perturbative expansion. We use these parameters to extract $|{V}_{\mathrm{cb}}|$ from the world average of the semileptonic width and find $|{V}_{\mathrm{cb}}|=(40.8\ifmmode\pm\else\textpm\fi{}{0.5}_{{\ensuremath{\Gamma}}_{\mathrm{sl}}}\ifmmode\pm\else\textpm\fi{}{0.4}_{({\ensuremath{\lambda}}_{1},\overline{\ensuremath{\Lambda}}{)}_{\mathrm{exp}}}\ifmmode\pm\else\textpm\fi{}{0.9}_{\mathrm{th}})\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}.$ In addition, we extract the short range b-quark mass ${m}_{b}^{1\mathrm{S}}=(4.82\ifmmode\pm\else\textpm\fi{}{0.07}_{\mathrm{exp}}\ifmmode\pm\else\textpm\fi{}{0.11}_{\mathrm{th}})\mathrm{GeV}{/c}^{2}.$ Finally, we discuss the implications of our measurements for the theoretical understanding of inclusive semileptonic processes.Color-singlet gauge bosons with renormalizable couplings to quarks but not to leptons must interact with additional fermions ("anomalons") required to cancel the gauge anomalies. Analyzing the decays of such leptophobic bosons into anomalons, I show that they produce final states involving leptons at the LHC. Resonant production of a flavor-universal leptophobic $Z'$ boson leads to cascade decays via anomalons, whose signatures include a leptonically decaying $Z$, missing energy and several jets. A $Z'$ boson that couples to the right-handed quarks of the first and second generations undergoes cascade decays that violate lepton universality and include signals with two leptons and jets, or with a Higgs boson, a lepton, a $W$ and missing energy.
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