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1,116 results on '"E. Stephan"'

1. Measurement of polarization transfer in the quasi-elastic Ca40(e→,e′p→) process

Author

T. Kolar, P. Achenbach, M. Christmann, M.O. Distler, L. Doria, P. Eckert, A. Esser, C. Giusti, J. Geimer, P. Gülker, M. Hoek, P. Klag, J. Lichtenstadt, M. Littich, T. Manoussos, D. Markus, H. Merkel, M. Mihovilovič, J. Müller, U. Müller, J. Pätschke, S.J. Paul, E. Piasetzky, S. Plura, J. Pochodzalla, M. Požun, G. Ron, B.S. Schlimme, C. Sfienti, S. Stengel, E. Stephan, S. Strauch, C. Szyszka, S. Širca, M. Thiel, and A. Wilczek

Subjects
Physics, QC1-999
Abstract

Polarization transfer to a bound proton in polarized electron knock-out reactions, A(e→,e′p→), is a powerful tool to look for an in-medium modification of the bound proton. It requires comparison to calculations that consider the many-body effects accompanying the quasi-free process. We report here measured components Px′, Pz′, and their ratio Px′/Pz′, of polarization transfer to protons bound in Ca40, which is described well by the shell model and for which reliable calculations are available. While the calculations capture the essence of the data, our statistical precision allows us to observe deviations that cannot be explained by simple scaling, including by varying the proton electromagnetic form factor ratio GE/GM. We further explore the deviations of the ratio of the polarization transfer components from that of a free proton, (Px′/Pz′)A/(Px′/Pz′)H, and its dependence on the bound-proton virtuality.

Published
2023
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2. Corrigendum to 'Isoscalar single-pion production in the region of Roper and d⁎(2380) resonances' [Phys. Lett. B 774 (2017) 599]

Author

P. Adlarson, W. Augustyniak, W. Bardan, M. Bashkanov, F.S. Bergmann, M. Berłowski, H. Bhatt, A. Bondar, M. Büscher, H. Calén, I. Ciepał, H. Clement, E. Czerwiński, K. Demmich, R. Engels, A. Erven, W. Erven, W. Eyrich, P. Fedorets, K. Föhl, K. Fransson, F. Goldenbaum, A. Goswami, K. Grigoryev, C.-O. Gullström, L. Heijkenskjöld, V. Hejny, N. Hüsken, L. Jarczyk, T. Johansson, B. Kamys, G. Kemmerling, G. Khatri, A. Khoukaz, O. Khreptak, D.A. Kirillov, S. Kistryn, H. Kleines, B. Kłos, W. Krzemień, P. Kulessa, A. Kupść, A. Kuzmin, K. Lalwani, D. Lersch, B. Lorentz, A. Magiera, R. Maier, P. Marciniewski, B. Mariański, H.-P. Morsch, P. Moskal, H. Ohm, W. Parol, E. Perez del Rio, N.M. Piskunov, D. Prasuhn, D. Pszczel, K. Pysz, A. Pyszniak, J. Ritman, A. Roy, Z. Rudy, O. Rundel, S. Sawant, S. Schadmand, I. Schätti-Ozerianska, T. Sefzick, V. Serdyuk, B. Shwartz, K. Sitterberg, T. Skorodko, M. Skurzok, J. Smyrski, V. Sopov, R. Stassen, J. Stepaniak, E. Stephan, G. Sterzenbach, H. Stockhorst, H. Ströher, A. Szczurek, A. Trzciński, R. Varma, M. Wolke, A. Wrońska, P. Wüstner, A. Yamamoto, J. Zabierowski, M.J. Zieliński, J. Złomańczuk, P. Żuprański, and M. Żurek

Subjects
Physics, QC1-999
Published
2020
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3. Search for η mesic 3He with the WASA-at-COSY facility in the pd→3He2γ and pd→3He6γ reactions

Author

P. Adlarson, W. Augustyniak, W. Bardan, M. Bashkanov, S.D. Bass, M. Berłowski, A. Bondar, M. Büscher, H. Calén, I. Ciepał, H. Clement, E. Czerwiński, R. Engels, A. Erven, W. Erven, W. Eyrich, P. Fedorets, K. Föhl, K. Fransson, F. Goldenbaum, A. Goswami, K. Grigoryev, L. Heijkenskjöld, V. Hejny, S. Hirenzaki, L. Jarczyk, T. Johansson, B. Kamys, N.G. Kelkar, G. Kemmerling, A. Khreptak, D.A. Kirillov, S. Kistryn, H. Kleines, B. Kłos, W. Krzemień, P. Kulessa, A. Kupść, K. Lalwani, D. Lersch, B. Lorentz, A. Magiera, R. Maier, P. Marciniewski, B. Mariański, H.-P. Morsch, P. Moskal, H. Ohm, W. Parol, E. Perez del Rio, N.M. Piskunov, D. Prasuhn, D. Pszczel, K. Pysz, J. Ritman, A. Roy, O. Rundel, S. Sawant, S. Schadmand, I. Schätti–Ozerianska, T. Sefzick, V. Serdyuk, B. Shwartz, T. Skorodko, M. Skurzok, J. Smyrski, V. Sopov, R. Stassen, J. Stepaniak, E. Stephan, G. Sterzenbach, H. Stockhorst, H. Ströher, A. Szczurek, A. Trzciński, M. Wolke, A. Wrońska, P. Wüstner, A. Yamamoto, J. Zabierowski, M.J. Zieliński, J. Złomańczuk, P. Żuprański, and M. Żurek

Subjects
Physics, QC1-999
Abstract

We report on the experimental search for the bound state of an η meson and He3 nucleus performed using the WASA-at-COSY detector setup. In order to search for the η-mesic nucleus decay, the pd→3He2γ and pd→3He6γ channels have been analysed. These reactions manifest the direct decay of the η meson bound in a He3 nucleus. This non-mesonic decay channel has been considered for the first time. When taking into account only statistical errors, the obtained excitation functions reveal a slight indication for a possible bound state signal corresponding to a 3He-η nucleus width Γ above 20 MeV and binding energy Bs between 0 and 15 MeV. However, the determined cross sections are consistent with zero in the range of the systematic uncertainty. Therefore, as final result we estimate only the upper limit for the cross section of the η-mesic He3 nucleus formation followed by the η meson decay which varies between 2 nb and 15 nb depending on possible bound state parameters. Keywords: η-mesic nuclei, η meson

Published
2020
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4. Search for C violation in the decay η → π0e+e− with WASA-at-COSY

Author

P. Adlarson, W. Augustyniak, W. Bardan, M. Bashkanov, F.S. Bergmann, M. Berłowski, A. Bondar, M. Büscher, H. Calén, I. Ciepał, H. Clement, E. Czerwiński, K. Demmich, R. Engels, A. Erven, W. Erven, W. Eyrich, P. Fedorets, K. Föhl, K. Fransson, F. Goldenbaum, A. Goswami, K. Grigoryev, C.-O. Gullström, L. Heijkenskjöld, V. Hejny, N. Hüsken, L. Jarczyk, T. Johansson, B. Kamys, G. Kemmerling, G. Khatri, A. Khoukaz, A. Khreptak, D.A. Kirillov, S. Kistryn, H. Kleines, B. Kłos, W. Krzemień, P. Kulessa, A. Kupść, A. Kuzmin, K. Lalwani, D. Lersch, B. Lorentz, A. Magiera, R. Maier, P. Marciniewski, B. Mariański, H.-P. Morsch, P. Moskal, H. Ohm, W. Parol, E. Perez del Rio, N.M. Piskunov, D. Prasuhn, D. Pszczel, K. Pysz, A. Pyszniak, J. Ritman, A. Roy, Z. Rudy, O. Rundel, S. Sawant, S. Schadmand, I. Schätti-Ozerianska, T. Sefzick, V. Serdyuk, B. Shwartz, K. Sitterberg, T. Skorodko, M. Skurzok, J. Smyrski, V. Sopov, R. Stassen, J. Stepaniak, E. Stephan, G. Sterzenbach, H. Stockhorst, H. Ströher, A. Szczurek, A. Trzciński, M. Wolke, A. Wrońska, P. Wüstner, A. Yamamoto, J. Zabierowski, M.J. Zieliński, J. Złomańczuk, P. Żuprański, M. Żurek, and A. Wirzba

Subjects
Physics, QC1-999
Abstract

We report on the search for the rare decay η→π0e+e− which is of interest to study C violation in the electromagnetic interaction which would indicate contributions from physics beyond the Standard Model, since the allowed decay via a two-photon intermediate state is strongly suppressed. The experiment has been performed using the WASA-at-COSY installation, located at the COSY accelerator of the Forschungszentrum Jülich, Germany. In total 3×107 events of the reaction pd→3Heη have been recorded at an excess energy of Q=59.8MeV. Based on this data set the C parity violating decay η→π0γ⁎→π0e+e− via a single-photon intermediate state has been searched for, resulting in new upper limits of Γ(η→π0e+e−)/Γ(η→π+π−π0)

Published
2018
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5. Total and differential cross sections of η-production in proton–deuteron fusion for excess energies between Qη = 13 MeV and Qη = 81 MeV

Author

P. Adlarson, W. Augustyniak, W. Bardan, M. Bashkanov, F.S. Bergmann, M. Berłowski, A. Bondar, M. Büscher, H. Calén, I. Ciepał, H. Clement, E. Czerwiński, K. Demmich, R. Engels, A. Erven, W. Erven, W. Eyrich, P. Fedorets, K. Föhl, K. Fransson, F. Goldenbaum, A. Goswami, K. Grigoryev, C.-O. Gullström, L. Heijkenskjöld, V. Hejny, N. Hüsken, L. Jarczyk, T. Johansson, B. Kamys, G. Kemmerling, G. Khatri, A. Khoukaz, A. Khreptak, D.A. Kirillov, S. Kistryn, H. Kleines, B. Kłos, W. Krzemień, P. Kulessa, A. Kupść, A. Kuzmin, K. Lalwani, D. Lersch, B. Lorentz, A. Magiera, R. Maier, P. Marciniewski, B. Mariański, H.-P. Morsch, P. Moskal, H. Ohm, W. Parol, E. Perez del Rio, N.M. Piskunov, D. Prasuhn, D. Pszczel, K. Pysz, A. Pyszniak, J. Ritman, A. Roy, Z. Rudy, O. Rundel, S. Sawant, S. Schadmand, I. Schätti-Ozerianska, T. Sefzick, V. Serdyuk, B. Shwartz, K. Sitterberg, T. Skorodko, M. Skurzok, J. Smyrski, V. Sopov, R. Stassen, J. Stepaniak, E. Stephan, G. Sterzenbach, H. Stockhorst, H. Ströher, A. Szczurek, A. Trzciński, M. Wolke, A. Wrońska, P. Wüstner, A. Yamamoto, J. Zabierowski, M.J. Zieliński, J. Złomańczuk, P. Żuprański, M. Żurek, and C. Wilkin

Subjects
Physics, QC1-999
Abstract

New data on both total and differential cross sections of the production of η mesons in proton–deuteron fusion to He3η in the excess energy region 13.6MeV≤Qη≤80.9MeV are presented. These data have been obtained with the WASA-at-COSY detector setup located at the Forschungszentrum Jülich, using a proton beam at 15 different beam momenta between pp=1.60GeV/c and pp=1.74GeV/c. While significant structure of the total cross section is observed in the energy region 20MeV≲Qη≲60MeV, a previously reported sharp variation around Qη≈50MeV cannot be confirmed. Angular distributions show the typical forward-peaking that was noted earlier. For the first time, it is possible to study the development of these angular distributions with rising excess energy over a wide interval. Keywords: Meson production, Proton–deuteron interactions, η meson

Published
2018
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6. Importance of d-wave contributions in the charge symmetry breaking reaction dd→4Heπ0

Author

P. Adlarson, W. Augustyniak, W. Bardan, M. Bashkanov, F.S. Bergmann, M. Berłowski, A. Bondar, M. Büscher, H. Calén, I. Ciepał, H. Clement, E. Czerwiński, K. Demmich, R. Engels, A. Erven, W. Erven, W. Eyrich, P. Fedorets, K. Föhl, K. Fransson, F. Goldenbaum, A. Goswami, K. Grigoryev, C.-O. Gullström, C. Hanhart, L. Heijkenskjöld, V. Hejny, N. Hüsken, L. Jarczyk, T. Johansson, B. Kamys, G. Kemmerling, G. Khatri, A. Khoukaz, O. Khreptak, D.A. Kirillov, S. Kistryn, H. Kleines, B. Kłos, W. Krzemień, P. Kulessa, A. Kupść, A. Kuzmin, K. Lalwani, D. Lersch, B. Lorentz, A. Magiera, R. Maier, P. Marciniewski, B. Mariański, H.-P. Morsch, P. Moskal, H. Ohm, W. Parol, E. Perez del Rio, N.M. Piskunov, D. Prasuhn, D. Pszczel, K. Pysz, A. Pyszniak, J. Ritman, A. Roy, Z. Rudy, O. Rundel, S. Sawant, S. Schadmand, I. Schätti-Ozerianska, T. Sefzick, V. Serdyuk, B. Shwartz, K. Sitterberg, T. Skorodko, M. Skurzok, J. Smyrski, V. Sopov, R. Stassen, J. Stepaniak, E. Stephan, G. Sterzenbach, H. Stockhorst, H. Ströher, A. Szczurek, A. Trzciński, M. Wolke, A. Wrońska, P. Wüstner, A. Yamamoto, J. Zabierowski, M.J. Zieliński, J. Złomańczuk, P. Żuprański, and M. Żurek

Subjects
Physics, QC1-999
Abstract

This letter reports a first quantitative analysis of the contribution of higher partial waves in the charge symmetry breaking reaction dd→4Heπ0 using the WASA-at-COSY detector setup at an excess energy of Q=60MeV. The determined differential cross section can be parametrized as dσ/dΩ=a+bcos2⁡θ⁎, where θ⁎ is the production angle of the pion in the center-of-mass coordinate system, and the results for the parameters are a=(1.55±0.46(stat)+0.32−0.8(syst))pb/sr and b=(13.1±2.1(stat)−2.7+1.0(syst))pb/sr. The data are compatible with vanishing p-waves and a sizable d-wave contribution. This finding should strongly constrain the contribution of the Δ isobar to the dd→4Heπ0 reaction and is, therefore, crucial for a quantitative understanding of quark mass effects in nuclear production reactions. Keywords: Charge symmetry breaking, Deuteron–deuteron interactions, Pion production

Published
2018
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7. Isoscalar single-pion production in the region of Roper and d⁎(2380) resonances

Author

P. Adlarson, W. Augustyniak, W. Bardan, M. Bashkanov, F.S. Bergmann, M. Berłowski, H. Bhatt, A. Bondar, M. Büscher, H. Calén, I. Ciepał, H. Clement, E. Czerwiński, K. Demmich, R. Engels, A. Erven, W. Erven, W. Eyrich, P. Fedorets, K. Föhl, K. Fransson, F. Goldenbaum, A. Goswami, K. Grigoryev, C.-O. Gullström, L. Heijkenskjöld, V. Hejny, N. Hüsken, L. Jarczyk, T. Johansson, B. Kamys, G. Kemmerling, G. Khatri, A. Khoukaz, O. Khreptak, D.A. Kirillov, S. Kistryn, H. Kleines, B. Kłos, W. Krzemień, P. Kulessa, A. Kupść, A. Kuzmin, K. Lalwani, D. Lersch, B. Lorentz, A. Magiera, R. Maier, P. Marciniewski, B. Mariański, H.-P. Morsch, P. Moskal, H. Ohm, W. Parol, E. Perez del Rio, N.M. Piskunov, D. Prasuhn, D. Pszczel, K. Pysz, A. Pyszniak, J. Ritman, A. Roy, Z. Rudy, O. Rundel, S. Sawant, S. Schadmand, I. Schätti-Ozerianska, T. Sefzick, V. Serdyuk, B. Shwartz, K. Sitterberg, T. Skorodko, M. Skurzok, J. Smyrski, V. Sopov, R. Stassen, J. Stepaniak, E. Stephan, G. Sterzenbach, H. Stockhorst, H. Ströher, A. Szczurek, A. Trzciński, R. Varma, M. Wolke, A. Wrońska, P. Wüstner, A. Yamamoto, J. Zabierowski, M.J. Zieliński, J. Złomańczuk, P. Żuprański, and M. Żurek

Subjects
Single-pion production, Isoscalar part, Roper resonance, Dibaryon resonance, Physics, QC1-999
Abstract

Exclusive measurements of the quasi-free pn→ppπ− and pp→ppπ0 reactions have been performed by means of pd collisions at Tp=1.2 GeV using the WASA detector setup at COSY. Total and differential cross sections have been obtained covering the energy region Tp=0.95–1.3 GeV (s=2.3–2.46 GeV), which includes the regions of Δ(1232), N⁎(1440) and d⁎(2380) resonance excitations. From these measurements the isoscalar single-pion production has been extracted, for which data existed so far only below Tp=1 GeV. We observe a substantial increase of this cross section around 1 GeV, which can be related to the Roper resonance N⁎(1440), the strength of which shows up isolated from the Δ resonance in the isoscalar (Nπ)I=0 invariant-mass spectrum. No evidence for a decay of the dibaryon resonance d⁎(2380) into the isoscalar (NNπ)I=0 channel is found. An upper limit of 180 μb (90% C.L.) corresponding to a branching ratio of 9% has been deduced.

Published
2017
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8. Measurement of the ω→π+π−π0 Dalitz plot distribution

Author

P. Adlarson, W. Augustyniak, W. Bardan, M. Bashkanov, F.S. Bergmann, M. Berłowski, H. Bhatt, A. Bondar, M. Büscher, H. Calén, I. Ciepał, H. Clement, E. Czerwiński, K. Demmich, R. Engels, A. Erven, W. Erven, W. Eyrich, P. Fedorets, K. Föhl, K. Fransson, F. Goldenbaum, A. Goswami, K. Grigoryev, C.-O. Gullström, L. Heijkenskjöld, V. Hejny, N. Hüsken, L. Jarczyk, T. Johansson, B. Kamys, G. Kemmerling, F.A. Khan, G. Khatri, A. Khoukaz, O. Khreptak, D.A. Kirillov, S. Kistryn, H. Kleines, B. Kłos, W. Krzemień, P. Kulessa, A. Kupść, A. Kuzmin, K. Lalwani, D. Lersch, B. Lorentz, A. Magiera, R. Maier, P. Marciniewski, B. Mariański, H.-P. Morsch, P. Moskal, H. Ohm, E. Perez del Rio, N.M. Piskunov, D. Prasuhn, D. Pszczel, K. Pysz, A. Pyszniak, J. Ritman, A. Roy, Z. Rudy, O. Rundel, S. Sawant, S. Schadmand, I. Schätti-Ozerianska, T. Sefzick, V. Serdyuk, B. Shwartz, K. Sitterberg, T. Skorodko, M. Skurzok, J. Smyrski, V. Sopov, R. Stassen, J. Stepaniak, E. Stephan, G. Sterzenbach, H. Stockhorst, H. Ströher, A. Szczurek, A. Trzciński, R. Varma, M. Wolke, A. Wrońska, P. Wüstner, A. Yamamoto, J. Zabierowski, M.J. Zieliński, J. Złomańczuk, P. Żuprański, and M. Żurek

Subjects
Decays of other mesons, Meson–meson interactions, Light mesons, Physics, QC1-999
Abstract

Using the production reactions pd→He3ω and pp→ppω, the Dalitz plot distribution for the ω→π+π−π0 decay is studied with the WASA detector at COSY, based on a combined data sample of (4.408±0.042)×104 events. The Dalitz plot density is parametrised by a product of the P-wave phase space and a polynomial expansion in the normalised polar Dalitz plot variables Z and ϕ. For the first time, a deviation from pure P-wave phase space is observed with a significance of 4.1σ. The deviation is parametrised by a linear term 1+2αZ, with α determined to be +0.147±0.036, consistent with the expectations of ρ-meson-type final-state interactions of the P-wave pion pairs.

Published
2017
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9. Search for an isospin I=3 dibaryon

Author

P. Adlarson, W. Augustyniak, W. Bardan, M. Bashkanov, F.S. Bergmann, M. Berłowski, H. Bhatt, A. Bondar, M. Büscher, H. Calén, I. Ciepał, H. Clement, E. Czerwiński, K. Demmich, R. Engels, A. Erven, W. Erven, W. Eyrich, P. Fedorets, K. Föhl, K. Fransson, F. Goldenbaum, A. Goswami, K. Grigoryev, C.-O. Gullström, L. Heijkenskjöld, V. Hejny, N. Hüsken, L. Jarczyk, T. Johansson, B. Kamys, G. Kemmerling, F.A. Khan, G. Khatri, A. Khoukaz, O. Khreptak, D.A. Kirillov, S. Kistryn, H. Kleines, B. Kłos, W. Krzemień, P. Kulessa, A. Kupść, A. Kuzmin, K. Lalwani, D. Lersch, B. Lorentz, A. Magiera, R. Maier, P. Marciniewski, B. Mariański, H.-P. Morsch, P. Moskal, H. Ohm, E. Perez del Rio, N.M. Piskunov, D. Prasuhn, D. Pszczel, K. Pysz, A. Pyszniak, J. Ritman, A. Roy, Z. Rudy, O. Rundel, S. Sawant, S. Schadmand, I. Schätti-Ozerianska, T. Sefzick, V. Serdyuk, B. Shwartz, K. Sitterberg, T. Skorodko, M. Skurzok, J. Smyrski, V. Sopov, R. Stassen, J. Stepaniak, E. Stephan, G. Sterzenbach, H. Stockhorst, H. Ströher, A. Szczurek, A. Trzciński, R. Varma, M. Wolke, A. Wrońska, P. Wüstner, A. Yamamoto, J. Zabierowski, M.J. Zieliński, A. Zink, J. Złomańczuk, P. Żuprański, and M. Żurek

Subjects
Physics, QC1-999
Abstract

Various theoretical calculations based on QCD or hadronic interactions predict that in addition to the recently observed dibaryon resonance d⁎(2380) with I(JP)=0(3+) there should also exist a dibaryon resonance with mirrored quantum numbers I(JP)=3(0+). We report here on a search for such a NN-decoupled state in data on the pp→ppπ+π+π−π− reaction. Since no clear-cut evidence has been found, we give upper limits for the production cross section of such a resonance in the mass range 2280–2500 MeV. Keywords: Dibaryons, Four-pion production

Published
2016
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10. РЕЗУЛЬТАТЫ ФУНКЦИОНИРОВАНИЯ МЕЖДУНАРОДНОЙ АГРОМЕТЕОРОЛОГИЧЕСКОЙ И ПОЧВЕННО-ГИДРОЛОГИЧЕСКОЙ МОНИТОРИНГОВОЙ СЕТИ В ПРЕДЕЛАХ КУЛУНДИНСКОЙ РАВНИНЫ НА ЮГЕ ЗАПАДНОЙ СИБИРИ ЗА 2013-2015 ГГ.

Author

G. Schmidt, A. A. Bondarovich, V. V. Scherbinin, E. V. Ponkina, N. F. Harlamova, A. V. Matsyura, E. Stephan, P. Illiger, N. V. Rudev, and N. A. Kozhanov

Subjects
глобальные и региональные изменения климата, геоэкологический мониторинг, Кулундинская равнина., Biology (General), QH301-705.5
Abstract

Приведены результаты функционирования сети автоматических станций в сухой степи, климатического и почвенно-гидрологического мониторинга за вегетационные периоды 2013-2015 гг. Опубликованные региональные данные по значимым эколого-климатическим параметрам представляют интерес для экологов, физиологов растений и фермеров, работающих на Кулундинской равнине.

Published
2016
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11. Measurement of the np→npπ0π0 reaction in search for the recently observed d⁎(2380) resonance

Author

P. Adlarson, W. Augustyniak, W. Bardan, M. Bashkanov, F.S. Bergmann, M. Berłowski, H. Bhatt, A. Bondar, M. Büscher, H. Calén, I. Ciepał, H. Clement, D. Coderre, E. Czerwiński, K. Demmich, E. Doroshkevich, R. Engels, A. Erven, W. Erven, W. Eyrich, P. Fedorets, K. Föhl, K. Fransson, F. Goldenbaum, P. Goslawski, A. Goswami, K. Grigoryev, C.-O. Gullström, F. Hauenstein, L. Heijkenskjöld, V. Hejny, B. Höistad, N. Hüsken, L. Jarczyk, T. Johansson, B. Kamys, G. Kemmerling, F.A. Khan, A. Khoukaz, D.A. Kirillov, S. Kistryn, H. Kleines, B. Kłos, W. Krzemień, P. Kulessa, A. Kupść, A. Kuzmin, K. Lalwani, D. Lersch, B. Lorentz, A. Magiera, R. Maier, P. Marciniewski, B. Mariański, M. Mikirtychiants, H.-P. Morsch, P. Moskal, H. Ohm, I. Ozerianska, E. Perez del Rio, N.M. Piskunov, P. Podkopał, D. Prasuhn, A. Pricking, D. Pszczel, K. Pysz, A. Pyszniak, J. Ritman, A. Roy, Z. Rudy, S. Sawant, S. Schadmand, T. Sefzick, V. Serdyuk, B. Shwartz, R. Siudak, T. Skorodko, M. Skurzok, J. Smyrski, V. Sopov, R. Stassen, J. Stepaniak, E. Stephan, G. Sterzenbach, H. Stockhorst, H. Ströher, A. Szczurek, A. Täschner, A. Trzciński, R. Varma, G.J. Wagner, M. Wolke, A. Wrońska, P. Wüstner, P. Wurm, A. Yamamoto, J. Zabierowski, M.J. Zieliński, A. Zink, J. Złomańczuk, P. Żuprański, and M. Żurek

Subjects
Physics, QC1-999
Abstract

Exclusive measurements of the quasi-free np→npπ0π0 reaction have been performed by means of dp collisions at Td=2.27 GeV using the WASA detector setup at COSY. Total and differential cross sections have been obtained covering the energy region s=(2.35–2.46) GeV, which includes the region of the ABC effect and its associated d⁎(2380) resonance. Adding the d⁎ resonance amplitude to that for the conventional processes leads to a reasonable description of the data. The observed resonance effect in the total cross section is in agreement with the predictions of Fäldt and Wilkin as well with those of Albadajedo and Oset. The ABC effect, i.e. the low-mass enhancement in the π0π0-invariant mass spectrum, is found to be very modest – if present at all, which might pose a problem to some of its interpretations. Keywords: Two-pion production, ABC effect and resonance structure, Dibaryon resonance

Published
2015
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12. Charge symmetry breaking in dd→He4π0 with WASA-at-COSY

Author

P. Adlarson, W. Augustyniak, W. Bardan, M. Bashkanov, F.S. Bergmann, M. Berłowski, H. Bhatt, A. Bondar, M. Büscher, H. Calén, I. Ciepał, H. Clement, D. Coderre, E. Czerwiński, K. Demmich, E. Doroshkevich, R. Engels, A. Erven, W. Erven, W. Eyrich, P. Fedorets, K. Föhl, K. Fransson, F. Goldenbaum, P. Goslawski, A. Goswami, K. Grigoryev, C.-O. Gullström, C. Hanhart, F. Hauenstein, L. Heijkenskjöld, V. Hejny, B. Höistad, N. Hüsken, L. Jarczyk, T. Johansson, B. Kamys, G. Kemmerling, F.A. Khan, A. Khoukaz, D.A. Kirillov, S. Kistryn, H. Kleines, B. Kłos, W. Krzemień, P. Kulessa, A. Kupść, A. Kuzmin, K. Lalwani, D. Lersch, B. Lorentz, A. Magiera, R. Maier, P. Marciniewski, B. Mariański, M. Mikirtychiants, H.-P. Morsch, P. Moskal, H. Ohm, I. Ozerianska, E. Perez del Rio, N.M. Piskunov, P. Podkopał, D. Prasuhn, A. Pricking, D. Pszczel, K. Pysz, A. Pyszniak, C.F. Redmer, J. Ritman, A. Roy, Z. Rudy, S. Sawant, S. Schadmand, T. Sefzick, V. Serdyuk, B. Shwartz, R. Siudak, T. Skorodko, M. Skurzok, J. Smyrski, V. Sopov, R. Stassen, J. Stepaniak, E. Stephan, G. Sterzenbach, H. Stockhorst, H. Ströher, A. Szczurek, A. Täschner, A. Trzciński, R. Varma, M. Wolke, A. Wrońska, P. Wüstner, P. Wurm, A. Yamamoto, L. Yurev, J. Zabierowski, M.J. Zieliński, A. Zink, J. Złomańczuk, P. Żuprański, and M. Żurek

Subjects
Physics, QC1-999
Abstract

Charge symmetry breaking (CSB) observables are a suitable experimental tool to examine effects induced by quark masses on the nuclear level. Previous high precision data from TRIUMF and IUCF are currently used to develop a consistent description of CSB within the framework of chiral perturbation theory. In this work the experimental studies on the reaction dd→He4π0 have been extended towards higher excess energies in order to provide information on the contribution of p-waves in the final state. For this, an exclusive measurement has been carried out at a beam momentum of pd=1.2 GeV/c using the WASA-at-COSY facility. The total cross section amounts to σtot=(118±18stat±13sys±8ext) pb and first data on the differential cross section are consistent with s-wave pion production. Keywords: Charge symmetry breaking, Deuteron–deuteron interactions, Pion production

Published
2014
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13. Soil water regime and crop yields in relation to various technologies of cultivation in the Kulunda Steppe (Altai Krai)

Author

V. Beliaev, T. Meinel, L. Grunwald, G. Schmidt, A. A. Bondarovich, V. V. Scherbinin, E. V. Ponkina, A. V. Matsyura, E. Stephan, P. Illiger, N. A. Kozhanov, and N. V. Rudev

Subjects
global and regional climate change, geo-ecological monitoring, crop yields, agricultural technology, dry steppe, Kulunda Plain, Biology (General), QH301-705.5
Abstract

This article presents the results of crop yield in areas with different technologies of cultivation based on the network of automatic stations that provide data on climatic and soil-hydrological monitoring in the dry steppe during the vegetation period of May–September 2013–2016 . These data on regional ecological and climatic parameters are of great interest to the ecologists, plant physiologists, and farmers working in the Kulunda Plain (Altai Territory). We compared the following options for cropping technologies: the modern system, which is the "no-till", technology without autumn tillage;the intensive technology of deep autumn tillage by plough PG-3-5 at a depth of 22–24 cm. Cultivation of crops was carried out using the following scheme of crop rotation: the modern system: 1–2–3–4 (wheat – peas – wheat – rape); the intensive system: 5/6 – 7/8 – 9/10 (fallow – wheat – wheat). We believe that the use of modern technology in these conditions is better due to exchange between the different layers of soil. When the ordinary Soviet system , the so-called "plow sole" , was used , at a depth of 24 cm , we observed that this creates a water conductivity barrier that seems to preclude the possibility of lifting water from the lower horizons. Results of the study of infiltration of soil moisture at the depth of 30 and 60 cm have shown in some years the advantages of the modern technology over the ordinary Soviet system: in the version with the use of modern technology we can trace better exchange between the various horizons and , probably, moisture replenishment from the lower horizons. Differences in individual observation periods are comparatively large due to the redistribution of soil moisture, depending on the weather conditions, the crops used in the crop rotations, and cultivation techniques. Moreover, the average moisture reserves within the one meter layer did not show any significant differences during the growing seasons of 2013–2016 . In terms of soil moisture usage and productive grain yield according to the four year experiment, the application of the modern technology with crop rotation "wheat – rape – wheat – peas" was more effective than the ordinary Soviet system with crop rotation "wheat – fallow – wheat – wheat". The four-year observation period is clearly insufficient to identify the advantages of the modern system, as during this time it is impossible to significantly improve soil quality indicators, which will continue to determine its water-retaining properties and moisture accumulation.

Published
2016
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24. Incorporating uncertainty within dynamic interoceptive learning

Author

Katja Brand, Toby Wise, Alexander J. Hess, Bruce R. Russell, Klaas E. Stephan, and Olivia K. Harrison

Abstract

Interoception, the perception of the internal state of the body, has been shown to be closely linked to emotions and mental health. Of particular interest are interoceptive learning processes that capture associations between environmental cues and body signals as a basis for making homeostatically relevant predictions about the future. Here we extended an interoceptive Breathing Learning Task (BLT) to incorporate continuous measures of prediction certainty, and tested its application using a Rescorla Wagner (RW) associative learning model. Sixteen healthy participants completed the continuous version of the BLT, where they were asked to predict the likelihood of breathing resistances. The task was modified from a previous version and required continuous, rather than binary predictions, in order to include a more precise measure of prediction certainty. The RW model was used to fit a learning rate to each participant’s continuous and binarised predictions, and was additionally extended to test whether learning rates differed according to stimuli valence. The empirical task data demonstrated excellent replicability compared to previously collected data using binary predictions, and the continuous model fits closely captured participant behaviour at the group level. The model extension to estimate different learning rates for negative (i.e. breathing resistance) and positive (i.e. no breathing resistance) trials indicated that learning rates did not significantly differ according to stimuli nature. Furthermore, examining the relationship between estimates of prediction certainty and learning rates with interoceptive and mental health questionnaires demonstrated that fatigue severity was related to both prediction certainty and learning rate, and anxiety sensitivity was related to prediction certainty. The updated task and model show promise for future investigations into interoceptive learning and potential links to mental health.

Published
2023

28. The Precision in Psychiatry (PIP) study: Testing an internet-based methodology for accelerating research in treatment prediction and personalisation

Author

Chi Tak Lee, Jorge Palacios, Derek Richards, Anna K. Hanlon, Kevin Lynch, Siobhan Harty, Nathalie Claus, Lorraine Swords, Veronica O’Keane, Klaas E Stephan, and Claire M Gillan

Subjects
Big data, Psychiatry and Mental health, Treatment response, Treatment outcomes, Treatment prediction, Mental health treatments, Internet-based methodology, Internet-delivered cognitive behavioural therapy, Antidepressant
Abstract

Background: Evidence-based treatments for depression exist but not all patients benefit from them. Efforts to develop predictive models that can assist clinicians in allocating treatments are ongoing, but there are major issues with acquiring the volume and breadth of data needed to train these models. We examined the feasibility, tolerability, patient characteristics, and data quality of a novel protocol for internet-based treatment research in psychiatry that may help advance this field. Methods: A fully internet-based protocol was used to gather repeated observational data from patient cohorts receiving internet-based cognitive behavioural therapy (iCBT) (N = 600) or antidepressant medication treatment (N = 110). At baseline, participants provided > 600 data points of self-report data, spanning socio-demographics, lifestyle, physical health, clinical and other psychological variables and completed 4 cognitive tests. They were followed weekly and completed another detailed clinical and cognitive assessment at week 4. In this paper, we describe our study design, the demographic and clinical characteristics of participants, their treatment adherence, study retention and compliance, the quality of the data gathered, and qualitative feedback from patients on study design and implementation. Results: Participant retention was 92% at week 3 and 84% for the final assessment. The relatively short study duration of 4 weeks was sufficient to reveal early treatment effects; there were significant reductions in 11 transdiagnostic psychiatric symptoms assessed, with the largest improvement seen for depression. Most participants (66%) reported being distracted at some point during the study, 11% failed 1 or more attention checks and 3% consumed an intoxicating substance. Data quality was nonetheless high, with near perfect 4-week test retest reliability for self-reported height (ICC = 0.97). Conclusions: An internet-based methodology can be used efficiently to gather large amounts of detailed patient data during iCBT and antidepressant treatment. Recruitment was rapid, retention was relatively high and data quality was good. This paper provides a template methodology for future internet-based treatment studies, showing that such an approach facilitates data collection at a scale required for machine learning and other data-intensive methods that hope to deliver algorithmic tools that can aid clinical decision-making in psychiatry., BMC Psychiatry, 23 (1), ISSN:1471-244X

Published
2023

32. Focus of attention modulates the heartbeat evoked potential

Author

Klaas E. Stephan, Katharina V. Wellstein, Frederike H. Petzschner, Cao Tri Do, Lilian A.E. Weber, Gina Paolini, University of Zurich, and Petzschner, Frederike H

Subjects
Predictive coding, Adult, Male, 2805 Cognitive Neuroscience, Heartbeat, media_common.quotation_subject, Cognitive Neuroscience, Interoception, Prediction error, Computational psychiatry, Computational psychosomatics, Active inference, Inference, Sensory system, 610 Medicine & health, Electroencephalography, Cognitive neuroscience, 050105 experimental psychology, 170 Ethics, Electrocardiography, Young Adult, 03 medical and health sciences, 0302 clinical medicine, Heart Rate, Perception, medicine, Humans, Attention, 0501 psychology and cognitive sciences, 10237 Institute of Biomedical Engineering, Evoked potential, Reactivity (psychology), Evoked Potentials, media_common, Cerebral Cortex, medicine.diagnostic_test, 05 social sciences, Focus (linguistics), Neurology, 2808 Neurology, Psychology, Neuroscience, 030217 neurology & neurosurgery
Abstract

Theoretical frameworks such as predictive coding suggest that the perception of the body and world – interoception and exteroception – involve intertwined processes of inference, learning, and prediction. In this framework, attention is thought to gate the influence of sensory information on perception. In contrast to exteroception, there is limited evidence for purely attentional effects on interoception. Here, we empirically tested if attentional focus modulates cortical processing of single heartbeats, using a newly-developed experimental paradigm to probe purely attentional differences between exteroceptive and interoceptive conditions in the heartbeat evoked potential (HEP) using EEG recordings. We found that the HEP is significantly higher during interoceptive compared to exteroceptive attention, in a time window of 524–620 ms after the R-peak. Furthermore, this effect predicted self-report measures of autonomic system reactivity. Our study thus provides direct evidence that the HEP is modulated by pure attention and suggests that this effect may provide a clinically relevant readout for assessing interoception., NeuroImage, 186, ISSN:1053-8119, ISSN:1095-9572

Published
2022

34. Ketamine affects prediction errors about statistical regularities: a computational single-trial analysis of the mismatch negativity

Author

Franz X. Vollenweider, Klaas E. Stephan, Christoph Mathys, André Schmidt, Andreea O. Diaconescu, Lilian A.E. Weber, Michael Kometer, and University of Zurich

Subjects
Male, Computer science, Inference, Mismatch negativity, Hierarchical database model, hierarchical Gaussian filter, 0302 clinical medicine, Models, Receptors, HGF, predictive coding, Evoked Potentials, Auditory, Research Articles, 0303 health sciences, General Neuroscience, 2800 General Neuroscience, Brain, Electroencephalography, Schizophrenia, Neurological, mismatch negativity, Auditory Perception, Evoked Potentials, Auditory, NMDA receptor, schizophrenia, Female, Ketamine, Single trial, Psychology, N-Methyl-D-Aspartate, Adult, Bayesian probability, Models, Neurological, Sensory system, 610 Medicine & health, Stimulus (physiology), Bayesian inference, Receptors, N-Methyl-D-Aspartate, 03 medical and health sciences, Young Adult, Double-Blind Method, medicine, Humans, 10237 Institute of Biomedical Engineering, 030304 developmental biology, Predictive coding, Motivation, Bayes Theorem, medicine.disease, Settore M-PSI/02 - Psicobiologia e Psicologia Fisiologica, Acoustic Stimulation, 10054 Clinic for Psychiatry, Psychotherapy, and Psychosomatics, Neuroscience, 030217 neurology & neurosurgery
Abstract

The auditory mismatch negativity (MMN) is significantly reduced in schizophrenia. Notably, a similar MMN reduction can be achieved with NMDA receptor (NMDAR) antagonists. Both phenomena have been interpreted as reflecting an impairment of predictive coding or, more generally, the “Bayesian brain” notion that the brain continuously updates a hierarchical model to infer the causes of its sensory inputs. Specifically, predictive coding views perceptual inference as an NMDAR-dependent process of minimizing hierarchical precision-weighted prediction errors (PEs). Disturbances of this putative process play a key role in hierarchical Bayesian theories of schizophrenia.Here, we provide empirical evidence for this clinical theory, demonstrating the existence of multiple, hierarchically related PEs in a “roving MMN” paradigm. We applied a computational model, the Hierarchical Gaussian Filter (HGF), to single-trial EEG data from healthy volunteers that received the NMDAR antagonist S-ketamine in a placebo-controlled, double-blind, within-subject fashion. Using an unrestricted analysis of the entire time-sensor space, our computational trial-by-trial analysis indicated that low-level PEs (about stimulus transitions) are expressed early (102-207ms post-stimulus), while high-level PEs (about transition probability) are reflected by later components (152-199ms, 215-277ms) of single-trial responses. Furthermore, we find that ketamine significantly diminished the expression of high-level PE responses, implying that NMDAR antagonism disrupts inference on abstract statistical regularities.Our findings are consistent with long-standing notions that NMDAR dysfunction may cause positive symptoms in schizophrenia by impairing hierarchical Bayesian inference about the world’s statistical structure. Beyond their relevance for schizophrenia, our results illustrate the potential of computational single-trial analyses for assessing potential disease mechanisms.

Published
2022

37. Matched-filter acquisition for BOLD fMRI.

Author

Lars Kasper, Maximilian Häberlin, Benjamin E. Dietrich, Simon Gross, Christoph Barmet, Bertram J. Wilm, S. Johanna Vannesjo, David O. Brunner, Christian C. Ruff, Klaas E. Stephan, and Klaas Paul Pruessmann

Published
2014
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38. Regression dynamic causal modeling for resting‐state fMRI

Author

Jakob Heinzle, Elliot S. Gershon, Albert R. Powers, Stefan Frässle, Brett A. Clementz, Klaas E. Stephan, Samuel J. Harrison, John A. Sweeney, Godfrey D. Pearlson, Carol A. Tamminga, and Matcheri S. Keshavan

Subjects
Adult, Connectomics, Adolescent, effective connectivity, Computer science, hierarchy, 050105 experimental psychology, Young Adult, 03 medical and health sciences, 0302 clinical medicine, Connectome, medicine, Humans, 0501 psychology and cognitive sciences, Radiology, Nuclear Medicine and imaging, generative model, connectomics, resting state, Research Articles, Causal model, Radiological and Ultrasound Technology, medicine.diagnostic_test, Resting state fMRI, 05 social sciences, Brain, Middle Aged, Models, Theoretical, Magnetic Resonance Imaging, Regression, Range (mathematics), Generative model, Neurology, regression dynamic causal modeling, Scalability, Regression Analysis, Neurology (clinical), Nerve Net, Anatomy, Functional magnetic resonance imaging, Algorithm, 030217 neurology & neurosurgery, Research Article
Abstract

“Resting‐state” functional magnetic resonance imaging (rs‐fMRI) is widely used to study brain connectivity. So far, researchers have been restricted to measures of functional connectivity that are computationally efficient but undirected, or to effective connectivity estimates that are directed but limited to small networks. Here, we show that a method recently developed for task‐fMRI—regression dynamic causal modeling (rDCM)—extends to rs‐fMRI and offers both directional estimates and scalability to whole‐brain networks. First, simulations demonstrate that rDCM faithfully recovers parameter values over a wide range of signal‐to‐noise ratios and repetition times. Second, we test construct validity of rDCM in relation to an established model of effective connectivity, spectral DCM. Using rs‐fMRI data from nearly 200 healthy participants, rDCM produces biologically plausible results consistent with estimates by spectral DCM. Importantly, rDCM is computationally highly efficient, reconstructing whole‐brain networks (>200 areas) within minutes on standard hardware. This opens promising new avenues for connectomics., “Resting‐state” functional magnetic resonance imaging (rs‐fMRI) is widely used to study brain connectivity. So far, researchers have been restricted to measures of functional connectivity that are computationally efficient but undirected, or to effective connectivity estimates that are directed but limited to small networks. Here, we show that a method recently developed for task‐fMRI—regression dynamic causal modeling (rDCM)—extends to rs‐fMRI and offers both directional estimates and scalability to whole‐brain networks.

Published
2021

43. Low predictive power of clinical features for relapse prediction after antidepressant discontinuation in a naturalistic setting

Author

Isabel M, Berwian, Julia G, Wenzel, Leonie, Kuehn, Inga, Schnuerer, Erich, Seifritz, Klaas E, Stephan, Henrik, Walter, and Quentin J M, Huys

Subjects
Adult, Male, Recurrence, Chronic Disease, Disease Progression, Humans, Female, Longitudinal Studies, Antidepressive Agents
Abstract

The risk of relapse after antidepressant medication (ADM) discontinuation is high. Predictors of relapse could guide clinical decision-making, but are yet to be established. We assessed demographic and clinical variables in a longitudinal observational study before antidepressant discontinuation. State-dependent variables were re-assessed either after discontinuation or before discontinuation after a waiting period. Relapse was assessed during 6 months after discontinuation. We applied logistic general linear models in combination with least absolute shrinkage and selection operator and elastic nets to avoid overfitting in order to identify predictors of relapse and estimated their generalisability using cross-validation. The final sample included 104 patients (age: 34.86 (11.1), 77% female) and 57 healthy controls (age: 34.12 (10.6), 70% female). 36% of the patients experienced a relapse. Treatment by a general practitioner increased the risk of relapse. Although within-sample statistical analyses suggested reasonable sensitivity and specificity, out-of-sample prediction of relapse was at chance level. Residual symptoms increased with discontinuation, but did not relate to relapse. Demographic and standard clinical variables appear to carry little predictive power and therefore are of limited use for patients and clinicians in guiding clinical decision-making.

Published
2022

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