Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userSearch for Charged Higgs Bosons in e+e- Collisions at sqrts(s) = 189-209 GeV
95
0
0.0
(
0
)
Authors
The OPAL collaboration
Ask ChatGPT about the research
No Arabic abstract
A search is made for charged Higgs bosons predicted by Two-Higgs-Doublet extensions of the Standard Model (2HDM) using electron-positron collision data collected by the OPAL experiment at sqrt(s)=189-209 GeV, corresponding to an integrated luminosity of approximately 600 pb-1. Charged Higgs bosons are assumed to be pair-produced and to decay into q qbar, tau nu or A W+-. No signal is observed. Model-independent limits on the charged Higgs-boson production cross section are derived by combining these results with previous searches at lower energies. Under the assumption BR(H+- -> tau nu) + BR(H+- -> qq)=1, motivated by general 2HDM type II models, excluded areas on the [m(H+-), BR(H+- -> tau nu)] plane are presented and charged Higgs bosons are excluded up to a mass of 76.3 GeV at 95% confidence level, independent of the branching ratio BR(H+- -> tau nu). A scan of the 2HDM type I model parameter space is performed and limits on the Higgs-boson masses m(H+-) and m(A) are presented for different choices of tan(beta).
rate research
Read More
In a study of the reaction e-e+ -> W-W+ with the DELPHI detector, the probabilities of the two W particles occurring in the joint polarisation states transverse-transverse (TT), longitudinal-transverse plus transverse-longitudinal (LT) and longitudinal-longitudinal (LL) have been determined using the final states WW -> l nu q qbar (l = e, mu). The two-particle joint polarisation probabilities, i.e. the spin density matrix elements rho_TT, rho_LT, rho_LL, are measured as functions of the W- production angle, theta_W-, at an average reaction energy of 198.2 GeV. Averaged over all cos(theta_W-), the following joint probabilities are obtained: rho_TT = (67 +/- 8)%, rho_LT = (30 +/- 8)%, rho_LL = (3 +/- 7)% . These results are in agreement with the Standard Model predictions of 63.0%, 28.9% and 8.1%, respectively. The related polarisation cross-sections sigma_TT, sigma_LT and sigma_LL are also presented.
We report the results of a search for the $X(1835)$ state in the process $e^+e^-to J/psi+X(1835)$ using a data sample of 672 fb$^{-1}$ collected with the Belle detector at and near the $Upsilon(4S)$ resonance at the KEKB asymmetric-energy $e^+e^-$ collider. No significant evidence is found for this process, and an upper limit is set on its cross section times the branching fraction: $sigma_{rm Born}(e^+e^- to J/psi X(1835)) cdot$ {${cal B}(X(1835)to ge 3$ charged tracks)} $< 1.3 {rm fb}$ at 90% confidence level.
We present a measurement of the azimuthal asymmetries of two charged pions in the inclusive process $e^+e^-rightarrow pipi X$ based on a data set of 62 $rm{pb}^{-1}$ at the center-of-mass energy $sqrt{s}=3.65$ GeV collected with the BESIII detector. These asymmetries can be attributed to the Collins fragmentation function. We observe a nonzero asymmetry, which increases with increasing pion momentum. As our energy scale is close to that of the existing semi-inclusive deep inelastic scattering experimental data, the measured asymmetries are important inputs for the global analysis of extracting the quark transversity distribution inside the nucleon and are valuable to explore the energy evolution of the spin-dependent fragmentation function.
We report the results of a search for a light pseudoscalar particle $a$ that couples to electrons and decays to $e^+e^-$ performed using the high-energy CERN SPS H4 electron beam. If such pseudoscalar with a mass $simeq 17$ MeV exists, it could explain the ATOMKI anomaly. We used the NA64 data samples collected in the visible mode configuration with total statistics corresponding to $8.4times 10^{10}$ electrons on target (EOT) in 2017 and 2018. In order to increase sensitivity to small coupling parameter $epsilon$ we used also the data collected in 2016-2018 in the invisible mode configuration of NA64 with a total statistics corresponding to $2.84times 10^{11}$ EOT. A thorough analysis of both these data samples in the sense of background and efficiency estimations was already performed and reported in our previous papers devoted to the search for light vector particles and axion-like particles (ALP). In this work we recalculate the signal yields, which are different due to different cross section and life time of a pseudoscalar particle $a$, and perform a new statistical analysis. As a result, the region of the two dimensional parameter space $m_a - epsilon$ in the mass range from 1 to 17.1 MeV is excluded. At the mass of the ATOMKI anomaly the values of $epsilon$ in the range $2.1 times 10^{-4} < epsilon < 3.2 times 10^{-4}$ are excluded.
We report the results of a first search for a doubly-charged $DDK$ bound state, denoted the $R^{++}$, in $Upsilon(1S)$ and $Upsilon(2S)$ inclusive decays and via direct production in $e^+e^-$ collisions at $sqrt{s}$ = 10.520, 10.580, and 10.867 GeV. The search uses data accumulated with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. No significant signals are observed in the $D^{+}D_{s}^{*+}$ invariant-mass spectra of all studied modes. The 90% credibility level upper limits on their product branching fractions in $Upsilon(1S)$ and $Upsilon(2S)$ inclusive decays (${cal B}(Upsilon(1S,2S) to R^{++} + anything) times {cal B}(R^{++} to D^{+} D_{s}^{*+})$), and the product values of Born cross section and branching fraction in $e^+e^-$ collisions ($sigma(e^+e^- to R^{++} + anything) times {cal B}(R^{++} to D^{+} D_{s}^{*+})$) at $sqrt{s}$ = 10.520, 10.580, and 10.867 GeV under different assumptions of $R^{++}$ masses varying from 4.13 to 4.17 GeV/$c^2$, and widths varying from 0 to 5 MeV are obtained.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
