Harald Merkel

Measurement of the Beam Normal Single-Spin Asymmetry of

Beam normal single-spin asymmetry in the elastic scattering of electrons is a direct probe for the two photon exchange. At the Mainz Mictrotron, this asymmetry has been measured for 12C in the Q2 range between 0.02 and 0.05 GeV2/c2. A 570 MeV continuous wave electrons beam was scattered on a carbon target and detected by two magnetic spectrometers. Quartz glass Cherenkov detectors located at the elastic line in the spectrometer’s focal plane were used to measure the amount of scattered electrons. The PMTs of which were read out with integrating current ADCs allowing for particle rates too high for counting. The resulting asymmetry shows a surprising deviation from the theoretical predictions.

^{12}

After the precise determination of the proton radius via the spectroscopy of muonic hydrogen, the proton radius puzzle arose in 2010. The extracted proton radius differs for over

C

7

Measurement of the proton form factor at very low Q2

standard deviations from the results obtained from electron scattering experiments and hydrogen spectroscopy. To help understanding this discrepancy an experiment has been performed at the Mainz Microtron (MAMI) in order to measure the proton form factors at the lowest possible values of Q

From deep inside to outer space: exploring neutron skins

^2

Hypernuclear Decay Pion Spectroscopy at Mainz Microtron

to date, using a method based on initial state radiation (ISR). In the following the problem will be briefly discussed and then the ISR approach will be described. Then the analysis will be presented and preliminary results will be shown. At the end an outlook for further exploiting the ISR method will be given.

Recent Studies of the Strangeness Physics at MAMI-C

M. Thiel∗1, S. Baunack1, D. Becker1, J. Diefenbach1, A.Esser1, M.I. Ferretti Bondy1, K.S. Kumar2,3, F.E. Maas1, H. Merkel1, U. Müller1, K.D. Paschke4, B.S. Schlimme1, C. Sfienti1, P.A. Souder5, and A. Tyukin1 1Institut für Kernphysik, Johannes Gutenberg-Universität Mainz, D-55099 Mainz, Germany 2Department of Physics, University of Massachusetts, MA 01003-9337, USA 3Department of Physics and Astronomy, Stony Brook University, NY 11794-3800, USA 4University of Virginia, Charlottesville, Virginia 22904, USA 5Syracuse University, Syracuse, New York 13244, USA E-mail: thiel@kph.uni-mainz.de

Neutral pion threshold production at Q 2 =0.05 GeV 2 /c 2 and chiral perturbation theory

Sho NAGAO1∗, Patrick ACHENBACH2, Naoki ARAI1, Carlos Ayerbe GAYOSO2, Ralph BOHM2, Olga BORODINA2,3, Damir BOSNAR4, Vakkas BOZKURT3, Luka DEBENJAK5, Michael O. DISTLER2, Anselm ESSER2, Ivica FRISCIC4, Yuu FUJII1, Toshiyuki GOGAMI1, Mar GOMEZ RODRIGUEZ2, Satoshi HIROSE1, Hiroki KANDA1, Masashi KANETA1, Eunhee KIM3, Junichiro KUSAKA1, Amur MARGARYAN6, Harald MERKEL2, Ulrich MULLER2, Satoshi N. NAKAMURA1, Josef POCHODZALLA2, Christophe RAPPOLD3, Joerg REINHOLD7, Takehiko R. SAITO2,3,8, Alicia Sanchez LORENTE8, Salvador Sanchez MAJOS2, Bjorn Soren SCHLIMME2, Matthias SCHOTH2, Florian SCHULZ2, Concettina SFIENTI2, Simon SIRCA5, Liguang TANG9, Michaela THIEL2, Kyo TSUKADA1, Daisuke UCHIYAMA1 A1 hypernuclear collaboration

Coherent π0 threshold production from the deuteron at Q2=0.1 GeV2/c2

Kyo Tsukada1, Patrick Achenbach2, Naoki Arai1, Carlos Ayerbe Gayoso2, Ralph Bohm2, Olga Borodina2,3, Damir Bosnar4, Vakkas Bozkurt3, Luka Debenjak5, Michael O. Distler2, Anselm Esser2, Ivica Friscic3, Yuu Fujii1, Toshiyuki Gogami1, Mar Gomez Rodriguez2, Osamu Hashimoto1, Satoshi Hirose1, Hiroki Kanda1, Masashi Kaneta1, Eunhee Kim3, Junichiro Kusaka1, Kazushige Maeda,1 Amur Margaryan6, Harald Merkel2, Ulrich Muller2, Sho Nagao1, Satoshi N. Nakamura1, Josef Pochodzalla2, Christophe Rappold3,7, Joerg Reinhold8, Takehiko R. Saito2,3,7, Alicia Sanchez Lorente7, Salvador Sanchez Majos2, Bjorn Soren Schlimme2, Matthias Schoth2, Florian Schulz2, Concettina Sfienti2, Simon Sirca5, Liguang Tang9, Michaela Thiel2 A1 hypernuclear collaboration