Over three quarters of a million, 4-m long Kuraray double-clad SCSF-78MJ (blue–green) scintillating fibres have been used in the construction of the GlueX electromagnetic barrel calorimeter, as part ...of the Hall D experimental program at Jefferson Lab. The response and quality of a random sample of 4750 of these fibres have been evaluated by employing a 373-nm UV LED to stimulate the fibres along their length and reading out the light using a spectrophotometer and a photodiode in order to extract the spectral response and the attenuation length, respectively. Single exponential fits to the spectral response in the 100–280cm distance from the light source yielded an average bulk attenuation length and standard deviation of (387±26)cm. Double-exponential fits to the spectral response over the entire 4-m length also allowed the extraction of long and short wavelength components at (486±54)cm and (75±22)cm, respectively. Finally, diameter uniformity measurements were carried out. The quality assurance results confirmed that the fibres were of high quality and complied with GlueX specifications.
We present a new limit on the production of a light dark-force mediator with the KLOE detector at DAΦNE. This boson, called U, has been searched for in the decay ϕ→ηU, U→e+e−, analyzing the decay ...η→π0π0π0 in a data sample of 1.7 fb−1. No structures are observed in the e+e− invariant mass distribution over the background. This search is combined with a previous result obtained from the decay η→π+π−π0, increasing the sensitivity. We set an upper limit at 90% C.L. on the ratio between the U boson coupling constant and the fine structure constant of α′/α<1.7×10−5 for 30<MU<400 MeV and α′/α⩽8×10−6 for the sub-region 50<MU<210 MeV. This result assumes the Vector Meson Dominance expectations for the ϕηγ⁎ transition form factor. The dependence of this limit on the transition form factor has also been studied.
A prototype plastic scintillating fibre based beam profile monitor was tested at the Heidelberg Ion Therapy Centre / \textit{Heidelberg Ionenstrahl Therapiezentrum} (HIT) in 2016 to determine its ...beam property reconstruction performance and the feasibility of further developing an expanded system. At HIT protons, helium, carbon, and oxygen ions are available for therapy and experiments. The beam can be scanned in two dimensions using fast deflection magnets. A tracking system is used to monitor beam position and to adjust scanner currents online. A new detector system with a finer granularity and without the drift time delay of the current MWPC system with a similar amount of material along the beamline would prove valuable in patient treatment. The sensitive detector components in the tested prototype detector are double-clad Kuraray SCSF-78MJ scintillating fibres with a diameter of 0.250~mm wound as a thin multi-layer ribbon. The scintillation light is detected at the end of the ribbon with Hamamatsu S11865-64 photodiode arrays with a pitch of 0.8~mm. The results shown in this paper include the linearity with respect to beam intensity, the RMS of the beam intensity as measured by two planes, along with the RMS of the mean position, and the measured beam width RMS. The Signal-to-Noise ratio of the current system is also measured as an indicator of potential performance. Additionally, the non-linear light yield of the scintillating fibres as measured by the photodiode arrays is compared to two models which describe the light yield as a function of the ion stopping power and Lorentz \(\beta\).
The ratio Rη=Γ(η→π+π−γ)/Γ(η→π+π−π0) has been measured by analysing 22 million ϕ→ηγ decays collected by the KLOE experiment at DAΦNE, corresponding to an integrated luminosity of 558 pb−1. The η→π+π−γ ...proceeds both via the ρ resonant contribution, and possibly a non-resonant direct term, connected to the box anomaly. Our result, Rη=0.1856±0.0005stat±0.0028syst, points out a sizable contribution of the direct term to the total width. The di-pion invariant mass for the η→π+π−γ decay could be described in a model-independent approach in terms of a single free parameter, α. The determined value of the parameter α is α=(1.32±0.08stat−0.09syst+0.10±0.02theo) GeV−2.
Abstract A search for $$C\!P$$ CP violation in charmless four-body decays of $${\varLambda } ^0_{b} $$ Λb0 and $${\varXi } ^0_{b} $$ Ξb0 baryons with a proton and three charged mesons in the final ...state is performed. To cancel out production and detection charge-asymmetry effects, the search is carried out by measuring the difference between the $$C\!P$$ CP asymmetries in a charmless decay and in a decay with an intermediate charmed baryon with the same particles in the final state. The data sample used was recorded in 2011 and 2012 with the LHCb detector and corresponds to an integrated luminosity of $$3 \text { fb} ^{-1} $$ 3fb-1 . A total of 18 $$C\!P$$ CP asymmetries are considered, either accounting for the full phase space of the decays or exploring specific regions of the decay kinematics. No significant $$C\!P$$ CP -violation effect is observed in any of the measurements.
Abstract Amplitude models are constructed to describe the resonance structure of $${D^{0}\rightarrow K^{-}\pi ^{+}\pi ^{+}\pi ^{-}}$$ D0→K-π+π+π- and $${D^{0} \rightarrow K^{+}\pi ^{-}\pi ^{-}\pi ...^{+}}$$ D0→K+π-π-π+ decays using pp collision data collected at centre-of-mass energies of 7 and 8 TeV with the LHCb experiment, corresponding to an integrated luminosity of 3.0 $$fb^{-1}$$ fb-1 . The largest contributions to both decay amplitudes are found to come from axial resonances, with decay modes $$D^{0} \rightarrow a_1(1260)^{+} K^{-}$$ D0→a1(1260)+K- and $$D^{0} \rightarrow K_1(1270/1400)^{+} \pi ^{-}$$ D0→K1(1270/1400)+π- being prominent in $${D^{0}\rightarrow K^{-}\pi ^{+}\pi ^{+}\pi ^{-}}$$ D0→K-π+π+π- and $$D^{0}\rightarrow K^{+}\pi ^{-}\pi ^{-}\pi ^{+}$$ D0→K+π-π-π+ , respectively. Precise measurements of the lineshape parameters and couplings of the $$a_1(1260)^{+}$$ a1(1260)+ , $$K_1(1270)^{-}$$ K1(1270)- and $$K(1460)^{-}$$ K(1460)- resonances are made, and a quasi model-independent study of the $$K(1460)^{-}$$ K(1460)- resonance is performed. The coherence factor of the decays is calculated from the amplitude models to be $$R_{K3\pi } = 0.459\pm 0.010\,(\mathrm {stat}) \pm 0.012\,(\mathrm {syst}) \pm 0.020\,(\mathrm {model})$$ RK3π=0.459±0.010(stat)±0.012(syst)±0.020(model) , which is consistent with direct measurements. These models will be useful in future measurements of the unitary-triangle angle $$\gamma $$ γ and studies of charm mixing and $$C\!P$$ CP violation.
A
bstract
We present a measurement of
η
meson production in photon-photon interactions produced by electron-positron beams colliding with
GeV. The measurement is done with the KLOE detector at the
ϕ
...-factory DAΦNE with an integrated luminosity of 0.24 fb
−1
. The
e
+
e
−
→
e
+
e
−
η
cross section is measured without detecting the out-going electron and positron, selecting the decays
η
→
π
+
π
−
π
0
and
η
→
π
0
π
0
π
0
. The most relevant background is due to
e
+
e
−
→
ηγ
when the monochromatic photon escapes detection. The cross section for this process is measured as
σ
(
e
+
e
−
→
ηγ
) = (856 ± 8
stat
± 16
syst
) pb. The combined result for the
e
+
e
−
→
e
+
e
−
η
cross section is
σ
(
e
+
e
−
→
e
+
e
−
η
) = (32.72 ± 1.27
stat
± 0.70
syst
) pb. From this we derive the partial width Γ(
η
→
γγ
) = (520 ± 20
stat
± 13
syst
) eV. This is in agreement with the world average and is the most precise measurement to date.
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