arXiv subjects

R. Baldini Ferroli

Publications and source records attributed to R. Baldini Ferroli.

At least 307 records · Page 17Linked to original sources

arXiv2018

Test beam results of a Cylindrical GEM detector for the BESIII experiment

Gas detector are very light instrument used in high energy physics to measure the particle properties: position and momentum. Through high electric field is possible to use the Gas Electron Multiplier (GEM) technology to detect the charged particles and to exploit their properties to construct a large area detector, such as the new IT for BESIII. The state of the art in the GEM production allows to create very large area GEM foils (up to 50x100 $\mathrm{cm}^2$) and thanks to the small thickness of these foils is it possible to shape it to the desired form: a Cylindrical Gas Electron Multiplier (CGEM) is then proposed. The innovative construction technique based on Rohacell, a PMI foam, will give solidity to cathode and anode with a very low impact on material budget. The entire detector is sustained by Permaglass rings glued at the edges. These rings are used to assembly the CGEM, together with a dedicated Vertical Insertion System and moreover they host the On-Detector electronic. The anode has been improved w.r.t. the state of the art through a jagged readout that minimize the inter-strip capacitance. The mechanical challenge of this detector requires a precision of the entire geometry within few hundreds of microns in the whole area. In this contribution an overview of the construction technique, the validation of this technique through the realization of a CGEM, and its first tests will be presented. These activities are performed within the framework of the BESIIICGEM Project (645664), funded by the European Commission in the action H2020-RISE-MSCA-2014.

physics.ins-det↗

arXiv2018

The new cylindrical GEM inner tracker of BESIII

The Cylindrical GEM-Inner Tracker (CGEM-IT) is the upgrade of the internal tracking system of the BESIII experiment. It consists of three layers of cylindrically-shaped triple GEMs, with important innovations with respect to the existing GEM detectors, in order to achieve the best performance with the lowest material budget. It will be the first cylindrical GEM running with analog readout inside a 1T magnetic field. The simultaneous measurement of both the deposited charge and the signal time will permit to use a combination of two algorithms to evaluate the spatial position of the charged tracks inside the CGEM-IT: the charge centroid and the micro time projection chamber modes. They are complementary and can cope with the asymmetry of the electron avalanche when running in magnetic field and with non-orthogonal incident tracks. To evaluate the behavior under different working settings, both planar chambers and the first cylindrical prototype have been tested during various test beams at CERN with 150 GeV/c muons and pions. This paper reports the results obtained with the two reconstruction methods and a comparison between the planar and cylindrical chambers.

physics.ins-det↗

arXiv2018

Test beam results with prototypes for the new Cylindrical GEM Inner Tracker of the BESIII experiment

A cylindrical GEM tracker is under construction in order to replace and improve the inner tracking system of the BESIII experiment. Tests with planar chamber prototypes were carried out on the H4 beam line of SPS (CERN) with muons of 150 GeV/c momentum, to evaluate the efficiency and resolution under different working conditions. The obtained efficiency was in the 96 - 98% range. Two complementary algorithms for the position determination were developed: the charge centroid and the micro-TPC methods. With the former, resolutions <100 micron and <200 micron were achieved without and with magnetic field, respectively. The micro-TPC improved these results. By the end of 2016, the first cylindrical prototype was tested on the same beam line. It showed optimal stability under different settings. The comparison of its performance with respect to the planar chambers is ongoing. Here, the results of the planar prototype tests will be addressed.

physics.ins-det↗

arXiv2018

Search for $h_{c}\rightarrowπ^+π^-J/ψ$ via $ψ(3686)\rightarrow π^0π^+π^-J/ψ$

Using a data sample of $448.1\times10^6$ $ψ(3686)$ events collected with the BESIII detector operating at the BEPCII, we perform search for the hadronic transition $h_c\rightarrowπ^+π^-J/ψ$ via $ψ(3686)\rightarrowπ^0h_c$. No signals of the transition are observed, and the upper limit on the product branching fraction $\mathcal{B}(ψ(3686)\rightarrowπ^0h_c)\mathcal{B}(h_c\rightarrowπ^+π^-J/ψ)$ at the 90% confidence level is determined to be $2.0\times10^{-6}$. This is the most stringent upper limit to date.

hep-ex↗

arXiv2018

Study of the decays $D^+\rightarrowη^{(\prime)} e^+ν_{e}$

The charm semileptonic decays $D^+\toηe^+ν_{e}$ and $D^+\toη'e^+ν_{e}$ are studied with a sample of $e^+e^-$ collision data corresponding to an integrated luminosity of 2.93 fb$^{-1}$ collected at $\sqrt{s}$ = 3.773 GeV with the BESIII detector. We measure the branching fractions for $D^+\toηe^+ν_{e}$ to be $(10.74\pm0.81\pm0.51)\times10^{-4}$, and for $D^+\toη'e^+ν_{e}$ to be $(1.91\pm0.51\pm0.13)\times10^{-4}$, where the uncertainties are statistical and systematic, respectively. In addition, we perform a measurement of the form factor in the decay $D^+\toηe^+ν_{e}$. All the results are consistent with those obtained by the CLEO-c experiment.

hep-ex↗

arXiv2018

Measurement of absolute branching fraction of the inclusive decay $Λ_{c}^{+} \to Λ+ X$

Based on an $e^+e^-$ collision data sample corresponding to an integrated luminosity of 567$\,\rm{pb}^{-1}$ taken at the center-of-mass energy of $\sqrt{s} = 4.6$ GeV with the BESIII detector, we measure the absolute branching fraction of the inclusive decay $Λ_{c}^{+} \to Λ+ X$ to be $\mathcal{B}(Λ_{c}^{+} \to Λ+ X)=(38.2^{+2.8}_{-2.2}\pm0.8)\%$ using the double-tag method, where $X$ refers to any possible final state particles. In addition, we search for direct CP violation in the charge asymmetry of this inclusive decay for the first time, and obtain $\mathcal{A}_{CP} \equiv \frac{\mathcal{B}(Λ_{c}^{+} \to Λ+ X)-\mathcal{B}(\barΛ_{c}^{-} \to \barΛ + X)}{\mathcal{B}(Λ_{c}^{+} \to Λ+ X)+\mathcal{B}(\barΛ_{c}^{-} \to \barΛ + X)} = (2.1^{+7.0}_{-6.6}\pm1.4)\%$, a statistically limited result with no evidence of CP violation.

hep-ex↗

arXiv2018

Search for Baryon and Lepton Number Violation in $J/ψ\toΛ_c^+e^-+c.c.$

Using $1.31\times10^9$ $J/ψ$ events collected by the BESIII detector at the Beijing Electron Positron Collider, we search for the process $J/ψ\toΛ_c^+e^-+c.c.$ for the first time. In this process, both baryon and lepton number conservation is violated. No signal is found and the upper limit on the branching fraction $\mathcal{B}(J/ψ\toΛ_c^+e^-+c.c.)$ is set to be $6.9\times10^{-8}$ at the 90\% Confidence Level.

hep-ex↗

arXiv2018

Observation of the Semileptonic Decay $D^0 \to a_0(980)^- e^+ ν_e$ and Evidence for $D^+ \to a_0(980)^0 e^+ ν_e$

Using an $e^+e^-$ collision data sample of 2.93 fb$^{-1}$ collected at a center-of-mass energy of 3.773 GeV by the BESIII detector at BEPCII, we report the observation of $D^0 \to a_0(980)^- e^+ ν_e$ and evidence for $D^+ \to a_0(980)^0 e^+ ν_e~$ with significances of $6.4σ$ and $2.9σ$, respectively. The absolute branching fractions are determined to be $\mathcal{B}(D^0 \to a_0(980)^- e^+ ν_e)\times\mathcal{B}(a_0(980)^- \to ηπ^-) = (1.33_{-0.29}^{+0.33}({\rm stat})\pm0.09({\rm syst}))\times10^{-4}~$ and $\mathcal{B}(D^+ \to a_0(980)^0 e^+ ν_e)\times\mathcal{B}(a_0(980)^0 \to ηπ^0) = (1.66_{-0.66}^{+0.81}({\rm stat})\pm0.11({\rm syst}))\times10^{-4}~$. An upper limit of $\mathcal{B}(D^+ \to a_0(980)^0 e^+ ν_e)\times\mathcal{B}(a_0(980)^0 \to ηπ^0)<3.0\times10^{-4}~$ is also determined at the $90\%~$ confidence level.

hep-ex↗

arXiv2018

Observation of $e^{+}e^{-} \to ϕχ_{c1}$ and $ϕχ_{c2}$ at $\sqrt{s}$=4.600 GeV

Using a data sample collected with the BESIII detector operating at the BEPCII storage ring at a center-of-mass energy of $\sqrt{s}=4.600$ GeV, we search for the production of $e^{+}e^{-} \to ϕχ_{c0,1,2}$ and the charmonium-like state $Y(4140)$ in the radiative transition $e^{+}e^{-} \to γY(4140)$ with $Y(4140)$ subsequently decaying into $ϕJ/ψ$. The processes $e^{+}e^{-} \to ϕχ_{c1}$ and $ϕχ_{c2}$ are observed for the first time, each with a statistical significance of more than 10σ, and the Born cross sections are measured to be $(4.2^{+1.7}_{-1.0}\pm 0.3)$ pb and $(6.7^{+3.4}_{-1.7}\pm 0.5)$ pb, respectively, where the first uncertainties are statistical and the second systematic. No significant signals are observed for $e^{+}e^{-} \to ϕχ_{c0}$ and $e^{+}e^{-} \to γY(4140)$ and upper limits on the Born cross sections at $90\%$ confidence level are provided at $\sqrt{s}=4.600$ GeV.

hep-ex↗

arXiv2018

Measurements of the Branching Fractions of the Singly-Cabibbo-Suppressed Decays $D^0\toωη$, $η^{(\prime)}π^0$ and $η^{(\prime)}η$

By analyzing a data sample of 2.93 fb$^{-1}$ collected at $\sqrt s=$ 3.773 GeV with the BESIII detector operated at the BEPCII storage rings, we measure the branching fractions ${\mathcal B}(D^0\toωη)=(2.15\pm0.17_{\rm stat.}\pm0.15_{\rm sys.})\times 10^{-3}$, ${\mathcal B}(D^0\toηπ^0)=(0.58\pm0.05_{\rm stat.}\pm0.05_{\rm sys.})\times 10^{-3}$, ${\mathcal B}(D^0\toη^\primeπ^0)=(0.93\pm0.11_{\rm stat.}\pm0.09_{\rm sys.})\times 10^{-3}$, ${\mathcal B}(D^0\toηη)=(2.20\pm0.07_{\rm stat.}\pm0.06_{\rm sys.})\times 10^{-3}$ and ${\mathcal B}(D^0\toη^\primeη)=(0.94\pm0.25_{\rm stat.}\pm0.11_{\rm sys.})\times 10^{-3}$. We note that ${\mathcal B}(D^0\to ωη)$ is measured for the first time and that ${\mathcal B}(D^0\to ηη)$ is measured with much improved precision.

hep-ex↗

arXiv2018

Study of two-photon decays of pseudoscalar mesons via $J/ψ$ radiative decays

Using a sample of $4.48\times10^{8}$ $ψ(3686)$ events collected with the BESIII detector at the BEPCII collider, we study the two-photon decays of the pseudoscalar mesons $π^0$, $η$, $η^\prime$, $η(1405)$, $η(1475)$, $η(1760)$, and $X(1835)$ in $J/ψ$ radiative decays using $ψ(3686)\toπ^{+}π^{-}J/ψ$ events. The $π^0$, $η$ and $η^\prime$ mesons are clearly observed in the two-photon mass spectra, and the branching fractions are determined to be $B(J/ψ\toγπ^{0}\to3γ)=(3.57\pm0.12\pm0.16)\times10^{-5}$, $B(J/ψ\toγη\to3γ)=(4.42\pm0.04\pm0.18)\times10^{-4}$, and $B(J/ψ\toγη'\to3γ)=(1.26\pm0.02\pm0.05)\times10^{-4}$, where the first errors are statistical and the second systematic. No clear signal for $η(1405)$, $η(1475)$, $η(1760)$ or $X(1835)$ is observed in the two-photon mass spectra, and upper limits at the $90\%$ confidence level on the product branching fractions are obtained.

hep-ex↗

arXiv2018

Measurements of absolute branching fractions for $D$ mesons decays into two pseudoscalar mesons

Using a data sample of $e^+e^-$ collision data with an integrated luminosity of 2.93 fb$^{-1}$ taken at the center-of-mass energy $\sqrt s= 3.773$~GeV with the BESIII detector operating at the BEPCII storage rings, we measure the absolute branching fractions of the two-body hadronic decays $D^+\to π^+π^0$, $K^+ π^0$, $π^+ η$, $K^+η$, $π^+η^\prime$, $K^+η^\prime$, $K_S^0 π^+$, $K_S^0 K^+$, and $D^0\to π^+ π^-$, $K^+ K^-$, $K^\mp π^\pm$, $K_S^0 π^0$, $K_S^0 η$, $K_S^0 η^\prime$. Our results are consistent with previous measurements within uncertainties. Among them, the branching fractions for $D^+\toπ^+π^0$, $K^+π^0$, $π^+η$, $π^+η^\prime$, $K_S^0 π^+$, $K_S^0 K^+$ and $D^0 \to K_S^0 π^0$, $K_S^0 η$, $K_S^0 η^\prime$ are determined with improved precision compared to the world average values.

hep-ex↗

arXiv2018

Observation of $e^{+}e^{-} \rightarrow K\bar{K}J/ψ$ at center-of-mass energies from 4.189 to 4.600 GeV

We investigate the process $e^{+}e^{-} \rightarrow K\bar{K}J/ψ$ at center-of-mass energies from 4.189 to 4.600 GeV using 4.7 fb$^{-1}$ of data collected by the BESIII detector at the BEPCII collider. The Born cross sections for the reactions $e^{+}e^{-} \rightarrow K^{+}K^{-}J/ψ$ and $K_{S}^{0} K_{S}^{0} J/ψ$ are measured as a function of center-of-mass energy. The energy dependence of the cross section for $e^{+}e^{-} \rightarrow K^{+}K^{-}J/ψ$ is shown to differ from that for $π^{+}π^{-}J/ψ$ in the region around the $Y(4260)$. In addition, there is evidence for a structure around 4.5 GeV in the $e^{+}e^{-} \rightarrow K^{+}K^{-}J/ψ$ cross section that is not present in $π^{+}π^{-}J/ψ$.

hep-ex↗

arXiv2018

Measurement of the matrix elements for the decays $η^{\prime}\rightarrowηπ^+π^-$ and $η^{\prime}\rightarrowηπ^0π^0$

Based on a sample of $1.31\times10^9$ $J/ψ$ events collected with the BESIII detector, the matrix elements for the decays $η^{\prime}\toηπ^{+}π^{-}$ and $η^{\prime}\toηπ^{0}π^{0}$ are determined using 351,016 $η^{\prime}\to(η\toγγ)π^+π^-$ and 56,249 $η^{\prime}\to(η\toγγ)π^0π^0$ events with background levels less than 1\%. Two commonly used representations are used to describe the Dalitz plot density. We find that an assumption of a linear amplitude does not describe the data well. A small deviation of the obtained matrix elements between $η^{\prime}\toηπ^{+}π^{-}$ and $η^{\prime}\toηπ^{0}π^{0}$ is probably caused by the mass difference between charged and neutral pions or radiative corrections. No cusp structure in $η^{\prime}\toηπ^{0}π^{0}$ is observed.

hep-ex↗

arXiv2018

Study of $η(1475)$ and $X(1835)$ in radiative $J/ψ$ decays to $γϕ$

The decay $J/ψ\rightarrow γγϕ$ is studied using a sample of $1.31 \times10^{9}$ $J/ψ$ events collected with the BESIII detector. Two structures around 1475 MeV/c$^2$ and 1835 MeV/c$^2$ are observed in the $γϕ$ invariant mass spectrum for the first time. With a fit on the $γϕ$ invariant mass, which takes into account the interference between the two structures, and a simple analysis of the angular distribution, the structure around 1475 MeV/c$^2$ is found to favor an assignment as the $η(1475)$ and the mass and width for the structure around 1835 MeV/c$^2$ are consistent with the $X(1835)$. The statistical significances of the two structures are $13.5 σ$ and $6.3 σ$, respectively. The results indicate that both $η(1475)$ and $X(1835)$ contain a sizeable $s\bar{s}$ component.

hep-ex↗

arXiv2018

Search for $ψ(3686)\to γη_c(η(1405))\to γπ^{+}π^{-}π^{0}$

Using a sample of $448.1\times10^{6}$ $ψ(3686)$ events collected with the BESIII detector, a search for the isospin violating decay $η_{c}\toπ^{+}π^{-}π^{0}$ via $ψ(3686)\toγη_{c}$ is presented. No signal is observed, and the upper limit on $\mathcal{B}(ψ(3686)\to γη_{c}\to γπ^{+}π^{-}π^{0} )$ is determined to be $1.6\times10^{-6}$ at the $90\%$ confidence level. In addition, a search for $η(1405)\to f_{0}(980)π^{0}$ in $ψ(3686)$ radiative decays is performed. No signal is observed, and the branching fraction $\mathcal{B}(ψ(3686)\toγη(1405)\to γf_{0}(980)π^{0}\toγπ^+π^-π^0 )$ is calculated to be less than $ 5.0\times10^{-7}$ at the $90\%$ confidence level.

hep-ex↗

arXiv2017

Observation of $χ_{c2}\toη'η'$ and $χ_{c0,2}\toηη'$

Using a sample of $447.9\times 10^6$ $ψ(3686)$ events collected with the BESIII detector in 2009 and 2012, we study the decays $χ_{c0,2}\to$ $η'η'$ and $ηη'$. The decays $χ_{c2}\toη'η'$, $χ_{c0}\toηη'$ and $χ_{c2}\toηη'$ are observed for the first time with statistical significances of $9.6σ$, $13.4σ$ and $7.5σ$, respectively. The branching fractions are determined to be $\mathcal{B}(χ_{c0}\toη'η') =(2.19\pm0.03\pm0.14)\times10^{-3}$, $\mathcal{B}(χ_{c2}\toη'η') = (4.76\pm0.56\pm0.38)\times10^{-5}$, $\mathcal{B}(χ_{c0}\toηη') = (8.92\pm0.84\pm0.65)\times10^{-5}$ and $\mathcal{B}(χ_{c2}\toηη') = (2.27\pm0.43\pm0.25)\times10^{-5}$, where the first uncertainties are statistical and the second systematic. The precision for the measurement of $\mathcal{B}(χ_{c0}\toη'η')$ is significantly improved compared to previous measurements. Based on the measured branching fractions, the role played by the doubly and singly Okubo-Zweig-Iizuka disconnected transition amplitudes for $χ_{c0,2}$ decays into pseudoscalar meson pairs can be clarified.

hep-ex↗

arXiv2017

Branching fraction measurement of $J/ψ\rightarrow K_S K_L$ and search for $J/ψ\rightarrow K_S K_S$

Using a sample of $1.31 \times 10^{9}$ $J/ψ$ events collected with the BESIII detector at the BEPCII collider, we study the decays of $J/ψ\rightarrow K_S K_L$ and $K_S K_S$. The branching fraction of$J/ψ\rightarrow K_S K_L$ is determined to be ${\cal B}(J/ψ\rightarrow K_S K_L)=(1.93\pm0.01~(\rm{stat.})\pm0.05~(\rm{syst.}))\times10^{-4}$, which significantly improves on previous measurements. No clear signal is observed for the $J/ψ\rightarrow K_S K_S$ process, and the upper limit at the 95% confidence level for its branching fraction is determined to be ${\cal B}(J/ψ\rightarrow K_S K_S)<1.4\times10^{-8}$, which improves on the previous searches by two orders in magnitude and reaches the order of the Einstein-Podolsky-Rosen expectation.

hep-ex↗