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Fig. 2. (p,e + ,e - ) invariant mass (left) and acceptance and efficiency corrected angular distribution in the CM frame (center), compared to the simulation (blue line) using the resonance model [5]. Right part: helicity angle distribtution (acceptance and eff. corrected).fitted by :a(1+ b cos 2 ) (b=1.11± 0.32) (blue line). quark model [8] is used instead of the constant magnetic form factor (G M =3), which illustrates the sensitivity of these data to the electromagnetic structure of the N- transition. The predictions of the OBE model [4] (shown as dashed line) are in pretty good agreement with the data, but the other OBE model [3] (full line) overestimates the data. The shape of the spectrum changes dramatically when going from p+p to n+p interactions. In the mass region between 0.15 and 0.35 GeV/c 2 , the yield is about a factor 9 higher in the n+p reaction with respect to the pp reaction, while only a factor 2 is expected for the Dalitz decay contribution due to the isospin factors. The resonance model simulation, which includes a small Dalitz decay contribution, due to the neutron Fermi momentum, widely underestimates the measured dilepton yield. In this simulation, is missing the nucleonnucleon bremsstrahlung contribution, which is known to be in the case of the pn system much larger than in the case of pp. However, no satisfactory agreement is achieved either with the OBE calculations, in particular with the model of [4], despite its good behaviour in the case of the pp data. The interpretation of the pn dilepton spectra is still the subject of theoretical investigations, related for example, to possible meson off-shell production by higher-lying resonances or contribution of processes beyond the quasi-free approximation. Exclusive pp ppe + e – reaction The identification of three particles (p,e + ,e - ) in the final state allows for the exclusive reconstruction of Δ Dalitz decay channel under two conditions: a) invariant mass M ee > 0.14 GeV/c 2 for rejection of the Δ + p decay followed by the 0 Dalitz decay; b) selection of the missing mass of (p,e + ,e - ), M miss pee, close to the proton mass, as a signature of the exclusive pp ppe + e - channel identification. The simulation using the resonance model is used to apply acceptance corrections to the measured events and finally deduce the Δ Dalitz decay branching ratio. The integrated yield for M ee > 0.14 GeV/c 2 is not sensitive to the N-Δ transition form factor model [8], so the main model-dependent uncertainty comes from the description of the angular distributions. The signal to background ratio ranges for M ee > 0.14 GeV/c 2 from 5 to 10 and the number of reconstructed signal pairs N signal e+e- ~200, after the 0.889 < M miss pee < 1.011 GeV/c 2 (3 ) selection. It is important to prove that the data reveal the Δ resonance properties despite the unavoidable smearing due to the proton not coming from the Δ decay. Firstly, the measured Δ invariant mass and angular production distribution (Fig. 2 left and center parts) are in good agreement with the simulation, which indicates the resonant origin of the observed events. Another useful quantity is the helicity angle, i.e. the angle between leptons in the * rest frame and the * itself, when both leptons and * are boosted to the Δ rest frame at first. Fig. 2 (right part) shows the acceptance and efficiency corrected helicity angle spectrum, which is anisotropic and in agreement with the 1+cos 2 distribution expected from QED, when neglecting the Coulomb transition amplitude. This is, again, the hint that the Δ Dalitz decay channel has been reconstructed. Considering statistical and systematic errors on the measured yields, which are respectively 9% and less than 20%, the branching ratio is in agreement with the value of 4.2 10 -5 predicted by the QED calculations. The comparison of the exclusive 3-prong analysis in p+p and quasi-free n+p at 1.25 GeV will shed more light on the nature of the e + e - pair excess (measured in np) and on the role of the N-N bremsstrahlung. References [1] G.Agakichiev et al. (HADES coll.), Phys. Lett. B663, 43 (2008),Phys. Rev. Lett. 98, 052302 (2007). [2] E. Bratkovskaya and W. Cassing, Nucl. Phys. A807, 214 (2008). [3] L. P. Kaptari and B. Kämpfer, Nucl. Phys. A764, 338 (2006). [4] R. Shyam and U. Mosel, Phys. Rev. C67, 065202 (2003). [5] G. Agakichiev et al. (HADES coll.), subm. to Phys. Lett. B. [6] I. Fröhlich et al., arXiv:0909.5373 [nucl-ex]. [7] Contribution to this report and references therein. [8] Q. Wan and F. Iachello, Int. J. Mod. Phys. A20, 1846 (2005). Q. Wan, Ph.D. thesis, Yale University, New Haven, USA, 2007. 33
Status of the HADES experiment (III): hadronic channels in elementary reactions IPNO Participation: J. L. Boyard, T. Hennino, T. Liu, E. Morinière, B. Ramstein, M. Sudol. Collaboration : CAS-Rez, FZR-Dresden, GSI-Darmstadt, INR-Moscow, INFN/LNSCatania, INFN/University-Milano, ITEP-Moscow, SIP/Jag. Univ-Cracow, JW Goethe Univ.-Frankfurt, JINR- Dubna, J Liebig Univ.-Giessen, LIP-Coimbra, TUM-München, Univ., Santiago de Compostela, Univ. of Cyprus-Nicosia, NPI-Rez, Univ. Valencia Les voies hadroniques sont mesurées en parallèle avec les voies de production de di-électrons dans les réactions élémentaires par la collaboration HADES. L’idée est de contraindre précisément les modèles utilisés pour décrire les différents sources de di-électrons et, en particulier, la décroissance Dalitz de la résonance Δ. Les données très précises fournissent aussi des informations sur les mécanismes de production et de décroissance du Δ. Les résultats de l’analyse des voies hadroniques (pp→np + et pp → pp 0 ) mesurées dans la réaction à 1.25 GeV sont présentés. Physics motivations HADES reported in the recent years di-electron production in nucleus-nucleus collisions around 1- 2 AGeV [1]. In the invariant mass region 0.15 GeV/ c 2
Page 1 and 2: EXOTIC NUCLEI STRUCTURE AND REACTIO
Page 3 and 4: in the spectra by analyzing their t
Page 5 and 6: were taken from ref. [5]. Concernin
Page 7 and 8: keV -ray with the particles and the
Page 9 and 10: the 605.9 keV line of the 74 Zn 2+
Page 11 and 12: Figure 2 a n d analysis. Figure 2 s
Page 13 and 14: ing particles was thus obtained by
Page 15 and 16: First p-p p collisions in the ALICE
Page 17 and 18: Quarkonia physics with ALICE IPNO P
Page 19 and 20: NA50 updated puzzle IPNO Participat
Page 21 and 22: Status of the HADES experiment (I):
Page 23: Status of the HADES experiments (II
Page 27 and 28: Hadron physics in pbar-p p annihila
Page 29 and 30: Hadron Electrodynamics IPNO Partici
Page 31 and 32: G0 experiment at Jefferson Lab. IPN
Page 33 and 34: GEp-III and GEp-2 at Jefferson Lab
Page 35 and 36: Exotic low mass narrow baryons from
Page 37 and 38: The PVA4 parity violation experimen
Page 39 and 40: Etude des Distributions de Partons
Page 41 and 42: Latest Results from GRAAL IPNO Part
Page 43 and 44: Persistence of the Polarization in
Page 45 and 46: The northern site of the Pierre Aug
Page 47 and 48: The Pierre Auger southern Observato
Page 49 and 50: In figure 4 we plot the differentia
Page 51 and 52: THEORETICAL PHYSICS Research in the
Page 53 and 54: transfer reaction, the 34 Si(d, 3 H
Page 55 and 56: Collective excitations with SKYRME
Page 57 and 58: Pairing and nuclear incompressibili
Page 59 and 60: Pairing properties in nuclei and in
Page 61 and 62: Evaporation-residue residue cross s
Page 63 and 64: Extending the VMI model: normal and
Page 65 and 66: Alpha particle condensation in nucl
Page 67 and 68: Collective Modes in Ultracold Trapp
Page 69 and 70: Exploring key unknown neutrino prop
Page 71 and 72: Relic astrophysical and cosmologica
Page 73 and 74: After a term by term Borel resummat
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Chiral expansions of the π 0 lifet
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IPNO Participation: H. Sazdjian Eff
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fer is used to extract f + (0). We
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cleon. The spectrum becomes strongl
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A pseudo Coulombian potential in D=
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The many-body problem with an energ
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The rotational spectrum and the att
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Z-identification of very heavy nucl
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The Pegase project, a new solid sur
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But at 80 keV total energy ( 200 eV
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Isospin effects on fragment and par
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Radial collective energy and fragme
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Latent heat of the phase transition
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Alpha-particle particle condensatio
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Fluo X: Deexcitation time measureme
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ENERGY AND ENVIRONMENT The increasi
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toe/cap/y which energy access inequ
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nides. A global comparison can be p
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3D coupling of Monte-Carlo neutroni
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Fission cross sections of actinides
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Studies and synthesis of specific m
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Chemistry and Electrochemistry of T
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function of temperature. The recent
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global electron number of the redox
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(D 0 /D)-1 ln complexes of Pa(V). I
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