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Hoistad, Bo
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Publications (10 of 47) Show all publications
Adlarson, P., Augustyniak, W., Bardan, W., Bashkanov, M., Bergmann, F. S., Berlowski, M., . . . Zurek, M. (2015). ABC effect and resonance structure in the double-pionic fusion to He-3. Physical Review C. Nuclear Physics, 91(1), 015201
Open this publication in new window or tab >>ABC effect and resonance structure in the double-pionic fusion to He-3
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2015 (English)In: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 91, no 1, p. 015201-Article in journal (Refereed) Published
Abstract [en]

Exclusive and kinematically complete measurements of the double pionic fusion to He-3 have been performed in the energy region of the so-called ABC effect, which denotes a pronounced low-mass enhancement in the pi pi-invariant mass spectrum. The experiments were carried out with the WASA detector setup at COSY (the cooler synchrotron at Forschungszentrum Julich). Similar to the observations in the basic pn -> d pi(0)pi(0) reaction and in the dd -> He-4 pi(0)pi(0) reaction, the data reveal a correlation between the ABC effect and a resonance-like energy dependence in the total cross section. Differential cross sections are well described by the hypothesis of d* resonance formation during the reaction process in addition to the conventional t-channel Delta Delta mechanism. The deduced d* resonance width can be understood from collision broadening due to Fermi motion of the nucleons in initial and final nuclei.

National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-246372 (URN)10.1103/PhysRevC.91.015201 (DOI)000348728100005 ()
Available from: 2015-03-05 Created: 2015-03-05 Last updated: 2017-12-04Bibliographically approved
Adlarsona, P., Augustyniak, W., Bardan, W., Bashkanov, M., Bergmann, F. S., Berlowski, M., . . . Zurek, M. (2015). Measurement of the np -> np pi(0)pi(0) reaction in search for the recently observed d* (2380) resonance. Physics Letters B, 743, 325-332
Open this publication in new window or tab >>Measurement of the np -> np pi(0)pi(0) reaction in search for the recently observed d* (2380) resonance
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2015 (English)In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 743, p. 325-332Article in journal (Refereed) Published
Abstract [en]

Exclusive measurements of the quasi-free np --> np pi(0)pi(0) reaction have been performed by means of dp collisions at T-d = 2.27 GeV using the WASA detector setup at COSY. Total and differential cross sections have been obtained covering the energy region root 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 Faldt and Wilkin as well with those of Albadajedo and Oset. The ABC effect, i.e. the low-mass enhancement in the pi(0)pi(0)-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
National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-253065 (URN)10.1016/j.physletb.2015.02.067 (DOI)000352147500050 ()
Available from: 2015-06-11 Created: 2015-05-20 Last updated: 2017-12-04Bibliographically approved
Babusci, D., Balwierz-Pytko, I., Bencivenni, G., Bloise, C., Bossi, F., Branchini, P., . . . Wolke, M. (2015). Study of the Dalitz decay phi -> eta e(+)e(-) with the KLOE detector. Physics Letters B, 742, 1-6
Open this publication in new window or tab >>Study of the Dalitz decay phi -> eta e(+)e(-) with the KLOE detector
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2015 (English)In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 742, p. 1-6Article in journal (Refereed) Published
Abstract [en]

We have studied the vector to pseudoscalar conversion decay phi -> eta e(+)e(-), with.. eta -> pi(0)pi(0)pi(0), with the KLOE detector at DA phi NE. The data set of 1.7 fb(-1) of e(+)e(-) collisions at root s similar to M-phi contains a clear conversion decay signal of similar to 31,000 events from which we measured a value of BR(phi -> eta e(+)e-) = (1.075 +/- 0.007 +/- 0.038) x 10(-4). The same sample is used to determine the transition form factor by a fit to the e(+)e(-) invariant mass spectrum, obtaining b(phi eta)=( 1.28 +/- 0.10(-0.08)(+0.09)) GeV-2, that improves by a factor of five the precision of the previous measurement and is in good agreement with VMD expectations.

Keywords
e(+)e(-) collisions, Conversion decay, Transition form factor
National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-251429 (URN)10.1016/j.physletb.2015.01.011 (DOI)000350555900001 ()
Available from: 2015-04-23 Created: 2015-04-17 Last updated: 2017-12-04Bibliographically approved
Adlarson, P., Augustyniak, W., Bardan, W., Bashkanov, M., Bergmann, F. S., Berlowski, M., . . . Zurek, M. (2014). Charge symmetry breaking in dd -> He-4 pi(0) with WASA-at-COSY. Physics Letters B, 739, 44-49
Open this publication in new window or tab >>Charge symmetry breaking in dd -> He-4 pi(0) with WASA-at-COSY
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2014 (English)In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 739, p. 44-49Article in journal (Refereed) Published
Abstract [en]

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 -> He-4 pi(0) 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 p(d) = 1.2GeV/c using the WASA-at-COSY facility. The total cross section amounts to sigma(tot) =(118 +/- 18(stat) +/- 13(sys) +/- 8(ext)) p band first data on the differential cross section are consistent with s-wave pion production.

Keywords
Charge symmetry breaking, Deuteron-deuteron interactions, Pion production
National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-241404 (URN)10.1016/j.physletb.2014.10.029 (DOI)000346002000006 ()
Available from: 2015-01-20 Created: 2015-01-12 Last updated: 2017-12-05Bibliographically approved
Adlarson, P., Augustyniak, W., Bardan, W., Bashkanov, M., Bergmann, F. S., Berlowski, M., . . . Zurek, M. (2014). Cross section ratio and angular distributions of the reaction p + d -> He-3 + eta at 48.8MeV and 59.8MeV excess energy. European Physical Journal A, 50(6), 100
Open this publication in new window or tab >>Cross section ratio and angular distributions of the reaction p + d -> He-3 + eta at 48.8MeV and 59.8MeV excess energy
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2014 (English)In: European Physical Journal A, ISSN 1434-6001, E-ISSN 1434-601X, Vol. 50, no 6, p. 100-Article in journal (Refereed) Published
Abstract [en]

We present new data for angular distributions and on the cross section ratio of the p+d -> He-3+eta reaction at excess energies of Q - 48.8MeV and Q - 59.8 MeV. The data have been obtained at the WASA-at-COSY experiment (Forschungszentrum Julich) using a proton beam and a deuterium pellet target. While the shape of obtained angular distributions show only a slow variation with the energy, the new results indicate a distinct and unexpected total cross section fluctuation between Q = 20MeV and Q = 60 MeV, which might indicate the variation of the production mechanism within this energy interval.

National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-229294 (URN)10.1140/epja/i2014-14100-4 (DOI)000338121900002 ()
Available from: 2014-08-06 Created: 2014-08-05 Last updated: 2017-12-05Bibliographically approved
Adlarson, P., Augustyniak, W., Bardan, W., Bashkanov, M., Bergmann, F. S., Berlowski, M., . . . Strakovsky, I. I. (2014). Evidence for a New Resonance from Polarized Neutron-Proton Scattering. Physical Review Letters, 112(20), 202301
Open this publication in new window or tab >>Evidence for a New Resonance from Polarized Neutron-Proton Scattering
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2014 (English)In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 112, no 20, p. 202301-Article in journal (Refereed) Published
Abstract [en]

Exclusive and kinematically complete high-statistics measurements of quasifree polarized (n) over right arrowp scattering have been performed in the energy region of the narrow resonancelike structure d* with I(J(P)) = 0(3(+)),M approximate to 2380 MeV, and Gamma approximate to 70 MeV observed recently in the double-pionic fusion channels pn -> d pi(0)pi(0) and pn -> d pi(+)pi(-). The experiment was carried out with the WASA detector setup at COSY having a polarized deuteron beam impinged on the hydrogen pellet target and utilizing the quasifree process (d) over right arrowp -> np + p(spectator). This allowed the np analyzing power, A(y), to be measured over a broad angular range. The obtained A(y) angular distributions deviate systematically from the current SAID SP07 NN partial-wave solution. Incorporating the new A(y) data into the SAID analysis produces a pole in the D-3(3) - (3)G(3) waves in support of the d* resonance hypothesis.

National Category
Subatomic Physics
Identifiers
urn:nbn:se:uu:diva-228474 (URN)10.1103/PhysRevLett.112.202301 (DOI)000336914800003 ()
Available from: 2014-07-15 Created: 2014-07-15 Last updated: 2017-12-05Bibliographically approved
Babuscih, D., Balwierz-Pytkog, I., Bencivenni, G., Bloise, C., Bossi, F., Branchinir, P., . . . Wolke, M. (2014). Measurement of the absolute branching ratio of the K+ -> pi(+) pi(-) pi(+) (gamma) decay with the KLOE detector. Physics Letters B, 738, 128-133
Open this publication in new window or tab >>Measurement of the absolute branching ratio of the K+ -> pi(+) pi(-) pi(+) (gamma) decay with the KLOE detector
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2014 (English)In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 738, p. 128-133Article in journal (Refereed) Published
Abstract [en]

The absolute branching ratio of the K+ -> pi(+) pi(-) pi(+) (gamma) decay, inclusive of final-state radiation, has been measured using similar to 17 million tagged K+ mesons collected with the KLOE detector at DA Phi NE, the Frascati phi-factory. The result is: BR(K+ -> pi(+) pi(-) pi(+) (gamma)) = 0.05565 +/- 0.00031(stat) +/- 0.00025(syst) a factor similar or equal to 5 more precise with respect to the previous result. This work completes the program of precision measurements of the dominant kaon branching ratios at KLOE.

Keywords
e(+) e(-) experiments, Kaon decays
National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-240116 (URN)10.1016/j.physletb.2014.09.033 (DOI)000344624900018 ()
Available from: 2015-01-08 Created: 2015-01-05 Last updated: 2017-12-05Bibliographically approved
Adlarson, P., Augustyniak, W., Bardan, W., Bashkanov, M., Bergmann, F. S., Berlowski, M., . . . Zurek, M. (2014). Measurement of the eta -> pi(+)pi(-)pi(0) Dalitz plot distribution. Physical Review C. Nuclear Physics, 90(4), 045207
Open this publication in new window or tab >>Measurement of the eta -> pi(+)pi(-)pi(0) Dalitz plot distribution
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2014 (English)In: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 90, no 4, p. 045207-Article in journal (Refereed) Published
Abstract [en]

The Dalitz plot distribution of the eta -> pi(+)pi(-)pi(0) decay is determined by using a data sample of 1.2 x 10(7) eta mesons from the pd -> He-3 eta reaction at 1 GeV collected by the WASA detector at COSY.

National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-238557 (URN)10.1103/PhysRevC.90.045207 (DOI)000344026900003 ()
Available from: 2014-12-17 Created: 2014-12-14 Last updated: 2017-12-05Bibliographically approved
Adlarson, P., Augustyniak, W., Bardan, W., Bashkanov, M., Bergmann, F. S., Berlowski, M., . . . Zurek, M. (2014). Neutron-proton scattering in the context of the d*(2380) resonance. Physical Review C. Nuclear Physics, 90(3), 035204
Open this publication in new window or tab >>Neutron-proton scattering in the context of the d*(2380) resonance
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2014 (English)In: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 90, no 3, p. 035204-Article in journal (Refereed) Published
Abstract [en]

New data on quasifree polarized neutron-proton scattering in the region of the recently observed d* resonance structure are obtained by exclusive and kinematically complete high-statistics measurements with WASA at COSY. This paper details the determination of the beam polarization, checks of the quasifree character of the scattering process, on all obtained Ay angular distributions and on the new partial-wave analysis, which includes the new data producing a resonance pole in D-3(3)-(3)G(3) coupled partial waves at (2380 +/- 10 - i40 +/- 5) MeV-in accordance with the d* dibaryon resonance hypothesis. The effect of the new partial-wave solution on the description of total and differential cross-section data as well as specific combinations of spin-correlation and spin-transfer observables available from COSY-ANKE measurements at T-d = 2.27 GeV is discussed.

National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-235170 (URN)10.1103/PhysRevC.90.035204 (DOI)000342139500007 ()
Available from: 2014-11-05 Created: 2014-10-29 Last updated: 2017-12-05Bibliographically approved
Babusci, D., Balwierz-Pytko, I., Bencivenni, G., Bloise, C., Bossi, F., Branchini, P., . . . Zdebik, J. (2014). Test of CPT and Lorentz symmetry in entangled neutral kaons with the KLOE experiment. Physics Letters B, 730, 89-94
Open this publication in new window or tab >>Test of CPT and Lorentz symmetry in entangled neutral kaons with the KLOE experiment
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2014 (English)In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 730, p. 89-94Article in journal (Refereed) Published
Abstract [en]

Neutral kaon pairs produced in phi decays in anti-symmetric entangled state can be exploited to search for violation of CPT symmetry and Lorentz invariance. We present an analysis of the CP-violating process phi -> KSKL -> pi(+)pi(-)pi(+)pi(-) based on 1.7 fb(-1) of data collected by the KLOE experiment at the Frascati phi-factory DA Phi NE. The data are used to perform a Measurement of the CPT-violating parameters Delta a(mu) for neutral kaons in the context of the Standard Model Extension framework. The parameters measured in the reference frame of the fixed stars are: Delta a(0) = (-6.0 +/- 7.7(stat)+/- 3.1(syst)) X 10(-18) GeV, Delta a(x) = (0.9 +/- 1.5(stat)+/- 0.6(syst)) X 10(-18) GeV, Delta a(y) = (-2.0 +/- 1.5(stat)+/- 0.5(syst)) X 10(-18) GeV, Delta a(z) = (3.1 +/- 1.7(stat)+/- 0.5(syst)) X 10(-18) GeV. These are presently the most precise measurements in the quark sector of the Standard Model Extension. (C) 2014 The Authors. Published by Elsevier B.V.

Keywords
CPT symmetry, Lorentz symmetry, Neutral kaons, phi-Factory
National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-224471 (URN)10.1016/j.physletb.2014.01.026 (DOI)000333506400017 ()
Available from: 2014-05-15 Created: 2014-05-13 Last updated: 2017-12-05Bibliographically approved
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