OBSERVATION OF $p\bar{p}$, $p\bar{\Lambda}$, $K^-\bar{\Lambda}$ NEAR-THRESHOLD ENHANCEMENT AT BES

2005 ◽  
Vol 20 (08n09) ◽  
pp. 1985-1989 ◽  
Author(s):  
◽  
HONGXUN YANG
Keyword(s):  
Mass Spectrum ◽  
Invariant Mass ◽  
Confidence Level ◽  
Invariant Mass Spectrum ◽  
Total Width ◽  
S Wave ◽  
Threshold Enhancement ◽  
Peak Mass ◽  
Near Threshold

We observe a narrow enhancement near 2mp in the invariant mass spectrum of [Formula: see text] pairs from radiative [Formula: see text] decays. In the case of S-wave fit, the peak mass is below 2mp at [Formula: see text] and the total width is Γ<30MeV at the 90% confidence level. And we also find near-threshold enhancement in the invariant mass spectrum of [Formula: see text] in [Formula: see text] decays. The mass is m=2075±12(stat)±5(syst)MeV and width is Γ=90±35(stat)±9(syst)MeV. A [Formula: see text] near-threshold enhancement is also studied and it has m=1.50~1.65GeV, Γ=70~110MeV with [Formula: see text].

OBSERVATION OF THE ABC EFFECT IN THE FIRST EXCLUSIVE MEASUREMENTS OF pn → dπ0π0

2007 ◽  
Vol 22 (02n03) ◽  
pp. 617-620 ◽  
Author(s):  
◽  
O. Khakimova ◽  
M. Bashkanov ◽  
T. Skorodko ◽  
C. Bargholtz ◽  
...  
Keyword(s):  
Mass Spectrum ◽  
Invariant Mass ◽  
Bound States ◽  
Fundamental System ◽  
Theoretical Models ◽  
Invariant Mass Spectrum ◽  
High Mass ◽  
Threshold Enhancement ◽  
Low Mass ◽  
Mass Enhancement

The reaction pn → dπ0π0 constitutes the most fundamental system for the study of the ABC effect - a puzzling threshold enhancement in the ππ invariant mass spectrum of the ππ system in double-pionic fusion to nuclear bound states. The first exclusive measurements of this reaction have now been carried out at CELSIUS-WASA. They exhibit a striking low-mass enhancement in the ππ invariant mass spectrum, prove it to be a σ-channel phenomenon and falsify conventional theoretical models, which predict an associated high-mass enhancement not present in the new exclusive data. In the kinematically complete data sample we observe a ΔΔ excitation, where the interaction between the two Δ obviously plays a crucial role for the generation of the ππ low-mass enhancement.

scholarly journals RECENT NA48/2 RESULTS ON Ke4 AND K3π DECAYS AND DETERMINATION OF THE ππ SCATTERING LENGTHS

2009 ◽  
Vol 24 (02n03) ◽  
pp. 488-492
Author(s):  
◽  
ANDREA BIZZETI
Keyword(s):  
Mass Spectrum ◽  
Invariant Mass ◽  
High Precision ◽  
Form Factors ◽  
Invariant Mass Spectrum ◽  
S Wave ◽  
Large Samples ◽  
Scattering Lengths

Large samples of K± → 3π and K± → π+π-e±ν (Ke4) decays have been collected by the NA48/2 experiment at CERN SPS. At the π+π- threshold, the π0π0 invariant mass spectrum of the decay K± → π±π0π0 xhibits a Wigner cusp, from which the S-wave ππ scattering lengths are extracted with high precision. The same scattering lengths are also independently determined from the accurate measurement of the form factors in the Ke4 decay K± → π+π-e±ν.

scholarly journals Observation of a Threshold Enhancement in thepΛ¯Invariant-Mass Spectrum

2004 ◽  
Vol 93 (11) ◽  
Author(s):  
M. Ablikim ◽  
J. Z. Bai ◽  
Y. Ban ◽  
J. G. Bian ◽  
X. Cai ◽  
...  
Keyword(s):  
Mass Spectrum ◽  
Invariant Mass ◽  
Invariant Mass Spectrum ◽  
Threshold Enhancement

LOW-MASS ππ ENHANCEMENT IN BARYONIC ππ PRODUCTION: ABC EFFECT REVISED BY EXCLUSIVE MEASUREMENTS

2007 ◽  
Vol 22 (02n03) ◽  
pp. 625-628 ◽  
Author(s):  
◽  
M. Bashkanov ◽  
O. Khakimova ◽  
T. Skorodko ◽  
C. Bargholtz ◽  
...  
Keyword(s):  
Mass Spectrum ◽  
Invariant Mass ◽  
Bound States ◽  
Invariant Mass Spectrum ◽  
High Mass ◽  
Crucial Importance ◽  
Threshold Enhancement ◽  
Model Predictions ◽  
Low Mass ◽  
Mass Enhancement

The ABC effect - a puzzling threshold enhancement in the ππ invariant mass spectrum of double-pionic fusion to nuclear bound states - has been investigated since 40 years by inclusive measurements without providing a conclusive interpretation. First exclusive measurements to this topic have now been carried out at CELSIUS-WASA. They confirm a huge ππ threshold enhancement, prove it to be of scalar-isoscalar nature, i.e., a σ-channel phenomenon and reveal the theoretically predicted high-mass enhancement in inclusive spectra to be of πππ rather than of ππ nature - falsifying thus corresponding model predictions for the ABC effect. From the kinematically complete data samples we infer that the interaction between the two Δ particles created in this process is of crucial importance.

scholarly journals BES RESULTS ON J/ψ DECAYS AND CHARMONIUM TRANSITIONS

2005 ◽  
Vol 20 (02n03) ◽  
pp. 445-454 ◽  
Author(s):  
◽  
FREDERICK A. HARRIS
Keyword(s):  
Mass Spectrum ◽  
Invariant Mass ◽  
Branching Fraction ◽  
Branching Fractions ◽  
Invariant Mass Spectrum ◽  
Pole Position ◽  
Hadronic Decays ◽  
Final States ◽  
S Wave ◽  
Upper Limits

Results are reported based on samples of 58 million J/ψ and 14 million ψ(2S) decays obtained by the BESII experiment. Improved branching fraction measurements are determined, including branching fractions for J/ψ→π+π-π0, ψ(2S)→π0J/ψ, ηJ/ψ, π0π0J/ψ, anything J/ψ, and ψ(2S)→γχc1, γχc2→γγJ/ψ. The decay J/ψ→ωπ+π- is studied. At low ππ mass, a large, broad peak due to the σ is observed, and its pole position is determined. Results are presented on ψ(2S) and J/ψ hadronic decays to [Formula: see text] and [Formula: see text] final states. No significant Θ(1540) signal, the pentaquark candidate, is observed, and upper limits are set. An enhancement near the mp+MΛ mass threshold is observed in the [Formula: see text] invariant mass spectrum from [Formula: see text] decays. It can be fit with an S-wave Breit-Wigner resonance with a mass m=2075±12 ( stat )±5 ( syst ) MeV and a width of Γ=90±35 ( stat )±9 ( syst ) MeV .

scholarly journals Upper limit on the η → π+π− branching fraction with the KLOE experiment

2020 ◽  
Vol 2020 (10) ◽  
Author(s):  
D. Babusci ◽  
◽  
M. Berlowski ◽  
C. Bloise ◽  
F. Bossi ◽  
...  
Keyword(s):  
Mass Spectrum ◽  
Invariant Mass ◽  
Confidence Level ◽  
Branching Fraction ◽  
Invariant Mass Spectrum ◽  
Upper Limit ◽  
Integrated Luminosity

Abstract Based on an integrated luminosity of 1.61 fb−1e+e− collision data collected with the KLOE detector at DAΦNE, the Frascati ϕ-factory, a search for the P- and CP-violating decay η → π+π− has been performed. Radiative ϕ → ηγ decay is exploited to access the η mesons. No signal is observed in the π+π− invariant mass spectrum, and the upper limit on the branching fraction at 90% confidence level is determined to be ℬ(η → π+π−) < 4.9 × 10−6, which is approximately three times smaller than the previous KLOE result. From the combination of these two measurements we get ℬ(η → π+π−) < 4.4 × 10−6 at 90% confidence level.

scholarly journals RECENT RESULTS ON LIGHT HADRON SPECTROSCOPY AT BESIII

2011 ◽  
Vol 02 ◽  
pp. 183-187
Author(s):  
◽  
Y. CHEN
Keyword(s):  
Mass Spectrum ◽  
Matrix Element ◽  
Direct Measurement ◽  
International Workshop ◽  
Charm Physics ◽  
Hadron Spectroscopy ◽  
Threshold Enhancement ◽  
Light Hadron ◽  
The Matrix ◽  
Near Threshold

Several measurements on light hadron spectroscopy have been achieved with Beijing Spectrometry III (BESIII). BESII results such as a near threshold enhancement on the [Formula: see text] invariants mass spectrum namely X(1860) and a resonance X(1835) have been confirmed with 225 million J/ψ data accumulated from June 12, 2009 to July 28, 2009. Along with some other preliminary BESIII results including observations of X(1870), X(2120) and X(2370); the first direct measurement of a0(980)/f0(980) mixing; and an improved measurement on the matrix element of decay η′ → ππη have been reported at the 4th international workshop on charm physics.

STUDY OF THE DIJET INVARIANT MASS IN W + JETS EVENTS BY THE DØ COLLABORATION

2012 ◽  
Vol 27 (01) ◽  
pp. 1230002
Author(s):  
JADRANKA SEKARIC
Keyword(s):  
Mass Spectrum ◽  
Invariant Mass ◽  
Experimental Verification ◽  
Hadron Collider ◽  
Mass Range ◽  
Invariant Mass Spectrum ◽  
Dijet Production ◽  
Dijet Mass ◽  
Two Jets ◽  
Recent Claim

The recent claim by the CDF Collaboration of a possible anomalous dijet resonance in their data required experimental verification from other hadron collider experiments. We present a study of the dijet invariant mass spectrum in events with two jets produced in association with a W→ℓν boson at the DØ experiment. We investigate the dijet mass range between 110 GeV /c2 and 170 GeV /c2 and find no evidence for any resonant dijet production.

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