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1.
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New results on the Be-8 anomaly
/ Krasznahorkay, A J (Debrecen, Inst. Nucl. Res.) ; Csatlós, M (Debrecen, Inst. Nucl. Res.) ; Csige, L (Debrecen, Inst. Nucl. Res.) ; Gulyás, J (Debrecen, Inst. Nucl. Res.) ; Hunyadi, M (Debrecen, Inst. Nucl. Res.) ; Ketel, T J (NIKHEF, Amsterdam) ; Krasznahorkay, A (CERN) ; Kuti, I (Debrecen, Inst. Nucl. Res.) ; Nagy, Á (Debrecen, Inst. Nucl. Res.) ; Nyakó, B M (Debrecen, Inst. Nucl. Res.) et al.
Recently, we measured the e+e− angular correlations in internal pair creation (IPC) for the M1 transitions depopulating the 17.6 and 18.15 MeV states in 8Be, and observed a peak-like deviation from the predicted IPC for the 18.15 MeV transition, but not for the 17.6 MeV one. To the best of our knowledge no nuclear physics related description of such deviation can be made. [...]
SISSA, 2017 - 10 p.
- Published in : PoS BORMIO2017 (2017) 036
Fulltext: PDF; External link: PoS server
In : 55th International Winter Meeting on Nuclear Physics, Bormio, Italy, 23 - 27 Jan 2017, pp.036
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2.
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On the creation of the 17 MeV X boson in the 17.6 MeV M1 transition of $^8Be$
/ Krasznahorkay, A J (Debrecen, Inst. Nucl. Res.) ; Csatlós, M (Debrecen, Inst. Nucl. Res.) ; Csige, L (Debrecen, Inst. Nucl. Res.) ; Gulyás, J (Debrecen, Inst. Nucl. Res.) ; Ketel, T J (NIKHEF, Amsterdam) ; Krasznahorkay, A (CERN ; MIT) ; Kuti, I (Debrecen, Inst. Nucl. Res.) ; Nagy, Á (Debrecen, Inst. Nucl. Res.) ; Nyakó, B M (Debrecen, Inst. Nucl. Res.) ; Sas, N (Debrecen, Inst. Nucl. Res.) et al.
Electron-positron angular correlations were remeasured for the 17.6 MeV $(J^π = 1^+ \to 0^+)$ ground state transition in $^8Be$ using an improved setup compared to one we used previously. Significant deviations from the internal pair creation was observed at large angles in the angular correlations, which supports that, in an intermediate step, a neutral isoscalar particle with a mass of 17.0±0.5 (stat)±0.5 (sys) $MeV/c^2$ and $J^π = 1^+$ was created..
2017 - 7 p.
- Published in : EPJ Web Conf. 142 (2017) 01019
Fulltext: PDF;
In : International Symposium Advances in Dark Matter and Particle Physics, Messina, Italy, 24 - 27 Oct 2016, pp.01019
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3.
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New experimental results for the 17 MeV particle created in $^8Be$
/ Krasznahorkay, A J (Debrecen, Inst. Nucl. Res.) ; Csatlós, M (Debrecen, Inst. Nucl. Res.) ; Csige, L (Debrecen, Inst. Nucl. Res.) ; Gulyás, J (Debrecen, Inst. Nucl. Res.) ; Hunyadi, M (Debrecen, Inst. Nucl. Res.) ; Ketel, T J (NIKHEF, Amsterdam) ; Krasznahorkay, A (CERN ; MIT) ; Kuti, I (Debrecen, Inst. Nucl. Res.) ; Nagy, Á (Debrecen, Inst. Nucl. Res.) ; Nyakó, B M (Debrecen, Inst. Nucl. Res.) et al.
Electron-positron angular correlations were remeasured for the 17.6 MeV $(J^π = 1^+ \to 0^+)$ ground state transition in $^8Be$ using an improved setup compared to the one we used previously. Significant deviations from the internal pair creation was observed at large angles in the angular correlations, which supports that, in an intermediate step, a neutral isoscalar particle with a mass of 17.0 ±0.2(stat) ±0.5(sys) $MeV/c^2$ and $J^π = 1^+$ was created..
2017 - 7 p.
- Published in : EPJ Web Conf. 137 (2017) 08010
Fulltext: PDF;
In : 12th Quark Confinement and the Hadron Spectrum, Thessaloniki, Greece, 29 Aug - 2 Sep 2016, pp.08010
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4.
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Observation of Anomalous Internal Pair Creation in $^8$Be
/ Krasznahorkay, A J (KLTE-ATOMKI) ; Csatlós, M (KLTE-ATOMKI) ; Csige, L (KLTE-ATOMKI) ; Gácsi, Z (KLTE-ATOMKI) ; Gulyás, J (KLTE-ATOMKI) ; Hunyadi, M (KLTE-ATOMKI) ; Ketel, T J (NIKHEF, Amsterdam) ; Krasznahorkay, A (KLTE-ATOMKI ; CERN) ; Kuti, I (KLTE-ATOMKI) ; Nyakó, B M (KLTE-ATOMKI) et al.
The electron–positron angular correlation was measured for the isoscalar magnetic dipole 18.15 MeV transition in 8Be. Significant, peak-like deviation was observed from the internal pair creation at Θ ≈ 140° in the angular correlation. [...]
2015 - 8 p.
- Published in : Acta Phys. Pol. Suppl. 8 (2015) 597
Acta Physica Polonica: PDF;
In : 22nd Nuclear Physics Workshop 'Marie & Pierre Curie': Essential Problems in Nuclear Physics, Kazimierz Dolny, Poland, 22 - 27 Sep 2015, pp.597
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5.
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6.
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Observation of Anomalous Internal Pair Creation in $^8$Be: A Possible Signature of a Light, Neutral Boson
/ Krasznahorkay, A. J. (Debrecen, Inst. Nucl. Res.) ; Csatlós, M. (KLTE-ATOMKI) ; Csige, L. (KLTE-ATOMKI) ; Gácsi, Z. (KLTE-ATOMKI) ; Gulyás, J. (KLTE-ATOMKI) ; Hunyadi, M. (KLTE-ATOMKI) ; Ketel, T.J. (NIKHEF, Amsterdam) ; Krasznahorkay, A. (KLTE-ATOMKI ; CERN) ; Kuti, I. (KLTE-ATOMKI) ; Nyakó, B.M. (KLTE-ATOMKI) et al.
Electron-positron angular correlations were measured for the isovector magnetic dipole 17.6 MeV state ($J^\pi=1^+$, $T=1$) $\rightarrow$ ground state ($J^\pi=0^+$, $T=0$) and the isoscalar magnetic dipole 18.15 MeV ($J^\pi=1^+$, $T=0$) state $\rightarrow$ ground state transitions in $^{8}$Be. Significant deviation from the internal pair creation was observed at large angles in the angular correlation for the isoscalar transition with a confidence level of $> 5\sigma$. [...]
arXiv:1504.01527.-
2016-01-26 - 5 p.
- Published in : Phys. Rev. Lett. 116 (2016) 042501
APS Open Access article: PDF; Fulltext: PDF; External link: Symmetry Magazine article
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7.
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A pair spectrometer for measuring multipolarities of energetic nuclear transitions
/ Gulyás, J. (Debrecen, Inst. Nucl. Res.) ; Ketel, T.J. (NIKHEF, Amsterdam) ; Krasznahorkay, A.J. (Debrecen, Inst. Nucl. Res.) ; Csatlós, M. (Debrecen, Inst. Nucl. Res.) ; Csige, L. (Debrecen, Inst. Nucl. Res.) ; Gácsi, Z. (Debrecen, Inst. Nucl. Res.) ; Hunyadi, M. (Debrecen, Inst. Nucl. Res.) ; Krasznahorkay, A. (CERN) ; Vitéz, A. (Debrecen, Inst. Nucl. Res.) ; Tornyi, T.G. (Debrecen, Inst. Nucl. Res.)
A multi-detector array has been designed and constructed for the simultaneous measurement of energy- and angular correlations of electron-positron pairs. Experimental results are obtained over a wide angular range for high-energy transitions in 16O, 12C and 8Be. [...]
arXiv:1504.00489.-
2016-02-01 - 8 p.
- Published in : Nucl. Instrum. Methods Phys. Res., A 808 (2016) 21-28
Fulltext: PDF; External link: Preprint
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8.
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Experimental investigation of the Landau-Pomeranchuk-Migdal effect in low-Z targets
/ Andersen, K.K. (Aarhus U.) ; Andersen, S.L. (Aarhus U.) ; Esberg, J. (CERN) ; Knudsen, H. (Aarhus U.) ; Mikkelsen, R.E. (Aarhus U.) ; Uggerhøj, U.I. (Aarhus U.) ; Wistisen, T.N. (Aarhus U.) ; Sona, P. (Florence U.) ; Mangiarotti, A. (Sao Paulo U.) ; Ketel, T.J. (Vrije U., Amsterdam)
/CERN NA63 Collaboration
In the CERN NA63 collaboration we have addressed the question of the potential inadequacy of the commonly used Migdal formulation of the Landau-Pomeranchuk-Migdal (LPM) effect by measuring the photon emission by 20 and 178 GeV electrons in the range 100 MeV - 4 GeV, in targets of LowDensityPolyEthylene (LDPE), C, Al, Ti, Fe, Cu, Mo and, as a reference target, Ta. For each target and energy, a comparison between simulated values based on the LPM suppression of incoherent bremsstrahlung is shown, taking multi-photon effects into account. [...]
arXiv:1309.5765.-
2013-10-15 - 8 p.
- Published in : Phys. Rev. D 88 (2013) 072007
APS published version, local copy: PDF; Fulltext: PDF; External link: Preprint
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9.
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Direct measurement of the formation length of photons
/ Andersen, Kristoffer K (Aarhus U.) ; Andersen, Søren L (Aarhus U.) ; Esberg, Jakob (Aarhus U.) ; Knudsen, Helge (Aarhus U.) ; Mikkelsen, Rune (Aarhus U.) ; Uggerhøj, Ulrik I (Aarhus U.) ; Sona, Pietro (Florence U.) ; Mangiarotti, Alessio (Coimbra U.) ; Ketel, Tjeerd J (Vrije U., Amsterdam) ; Ballestrero, Sergio (Johannesburg U.)
/CERN NA63 Collaboration
We report the first observation of a shoulder in the radiation spectrum from GeV electrons in a structured target consisting of two thin and closely spaced foils. The position of the shoulder depends on the target spacing and is directly connected to the finite formation length of a low-energy photon emitted by an ultrarelativistic electron. [...]
2012
- Published in : Phys. Rev. Lett. 108 (2012) 071802
APS published version, local copy: PDF;
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10.
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Distorted Coulomb field of the scattered electron
/ CERN NA63 Collaboration
Experimental results for the radiation emission from ultrarelativistic electrons in targets of 0.03%–5% radiation length is presented. For the thinnest targets, the radiation emission is in accordance with the Bethe-Heitler formulation of bremsstrahlung, the target acting as a single scatterer. [...]
2010
- Published in : Phys. Rev. D 81 (2010) 052003
APS published version, local copy: PDF;
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