اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدCombined limit on the production of a light gauge boson decaying into $mu^+mu^-$ and $pi^+pi^-$
100
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
We searched for the $mu^+mu^-$ decay of a light vector gauge boson, also known as dark photon, in the $e^+ e^- to mu^+ mu^- gamma_{rm ISR}$ process by means of the Initial State Radiation (ISR) method. We used 1.93~fb$^{-1}$ of data collected by the KLOE experiment at the DA$Phi$NE $phi$-factory. No structures have been observed over the irreducible $mu^+ mu^-$ background. A 90% CL limit on the ratio $varepsilon^2=alpha^{prime}/alpha$ between the dark coupling constant and the fine structure constant of $ 3times 10^{-6}-2times 10^{-7}$ has been set in the dark photon mass region between 519 MeV and 973 MeV. This new limit has been combined with the published result obtained investigating the hypothesis of the dark photon decaying into hadrons in $e^+ e^- to pi^+ pi^- gamma_{rm ISR}$ events. The combined 90% CL limit increases the sensitivity especially in the $rho-omega$ interference region and excludes $varepsilon^2$ greater than $(13-2)times 10^{-7}$. For dark photon masses greater than 600 MeV the combined limit is lower than 8~$times, 10^{-7}$ resulting more stringent than present constraints from other experiments.
قيم البحث
اقرأ أيضاً
Based on a sample of 225.3 million J/psi events accumulated with the BESIII detector at the BEPCII, the decays of eta to pi+pi-l+l- are studied via J/psi to gammaeta. A clear eta signal is observed in the pi+pi-e+e- mass spectrum, and the branching f
raction is measured to be BR(eta to pi+pi-e+e-) = (2.11pm0.12 (stat.)pm0.15 (syst.))times10^{-3}, which is in good agreement with theoretical predictions and the previous measurement, but is determined with much higher precision. No eta signal is found in the pi+ pi- mu+ mu- mass spectrum, and the upper limit is determined to be BR(eta to pi+ pi- mu+ mu-)<2.9times10^{-5} at the 90% confidence level.
A search for the rare decays $B_s^0 to pi^+pi^-mu^+mu^-$ and $B^0 to pi^+pi^-mu^+mu^-$ is performed in a data set corresponding to an integrated luminosity of 3.0 fb$^{-1}$ collected by the LHCb detector in proton-proton collisions at centre-of-mass
energies of 7 and 8 TeV. Decay candidates with pion pairs that have invariant mass in the range 0.5-1.3 GeV/$c^2$ and with muon pairs that do not originate from a resonance are considered. The first observation of the decay $B_s^0 to pi^+pi^-mu^+mu^-$ and the first evidence of the decay $B^0 to pi^+pi^-mu^+mu^-$ are obtained and the branching fractions, restricted to the dipion-mass range considered, are measured to be $mathcal{B}(B_s^0 to pi^+pi^-mu^+mu^-)=(8.6pm 1.5,({rm stat}) pm 0.7,({rm syst})pm 0.7,({rm norm}))times 10^{-8}$ and $mathcal{B}(B^0 to pi^+pi^-mu^+mu^-)=(2.11pm 0.51,({rm stat}) pm 0.15,({rm syst})pm 0.16,({rm norm}) )times 10^{-8}$, where the third uncertainty is due to the branching fraction of the decay $B^0to J/psi(to mu^+mu^-)K^*(890)^0(to K^+pi^-)$, used as a normalisation.
First observations of the rare decays $B^+rightarrow K^+pi^+pi^-mu^+mu^-$ and $B^+rightarrow phi K^+mu^+mu^-$ are presented using data corresponding to an integrated luminosity of $3.0,{fb}^{-1}$, collected by the LHCb experiment at centre-of-mass en
ergies of $7$ and $8mathrm{,TeV}$. The branching fractions of the decays are begin{eqnarray*} mathcal{B}(B^+rightarrow K^+pi^+pi^-mu^+mu^-) &=& (4.36,^{+0.29}_{-0.27},mathrm{(stat)}pm 0.21,mathrm{(syst)}pm0.18,mathrm{(norm)})times10^{-7}, mathcal{B}(B^+rightarrowphi K^+mu^+mu^-) &=& (0.82 ,^{+0.19}_{-0.17},mathrm{(stat)},^{+0.10}_{-0.04},mathrm{(syst)}pm0.27,mathrm{(norm)}) times10^{-7},end{eqnarray*} where the uncertainties are statistical, systematic, and due to the uncertainty on the branching fractions of the normalisation modes. A measurement of the differential branching fraction in bins of the invariant mass squared of the dimuon system is also presented for the decay $B^+rightarrow K^+pi^+pi^-mu^{+}mu^{-}$.
A search for the D0 to pi+ pi- mu+ mu- decay, where the muon pair does not originate from a resonance, is performed using proton-proton collision data corresponding to an integrated luminosity of 1.0 fb-1 recorded by the LHCb experiment at a centre-o
f-mass energy of 7 TeV. No signal is observed and an upper limit on the relative branching fraction with respect to the resonant decay mode D0 to pi+ pi- phi(to mu+ mu-), under the assumption of a phase-space model, is found to be B(D0 to pi+ pi- mu+ mu-)/B(D0 to pi+ pi- phi(to mu+ mu-)) < 0.96 at the 90% confidence level. The upper limit on the absolute branching fraction is evaluated to be B(D0 to pi+ pi- mu+ mu-) < 5.5 x 10-7 at 90% confidence level. This is the most stringent to date.
A search for non-resonant D+(s) to pi+mu+mu- and D+(s) to pi-mu+mu+ decays is performed using proton-proton collision data, corresponding to an integrated luminosity of 1.0 fb-1, at sqrt(s) = 7 TeV recorded by the LHCb experiment in 2011. No signals
are observed and the 90% (95%) confidence level (CL) limits on the branching fractions are B(D+ to pi+mu+mu-) < 7.3 (8.3) x 10-8, B(Ds+ to pi+mu+mu-) < 4.1 (4.8) x 10-7, B(D+ to pi-mu+mu+) < 2.2 (2.5) x 10-8, B(Ds+ to pi-mu+mu+) < 1.2 (1.4) x 10-7. These limits are the most stringent to date.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
