CGS18

Experimental studies of the dipole response of $fp$-shell nuclei via one-neutron transfer reactions

16 Jun 2026, 10:00

30m

Monterey, California (USA)

Oral Presentations Plenary

Speaker

Mark Spieker (Florida State University)

Description

In this invited contribution, I will present recent results from $(d,p)$ experiments performed with the Super-Enge Split-Pole Spectrograph at the John D. Fox Accelerator Laboratory of Florida State University [1] to study single-particle strengths in $fp$-shell nuclei [2-4]. After briefly highlighting the capabilities of the experimental setup [1,5], I will focus on three specific examples. First, I will provide a brief overview on our results obtained for the neutron-adding strengths in the $N=29$ isotone $^{53}$Cr [3], comparing to strengths measured earlier for $^{55}$Fe [6]. Then, I will pivot and focus on the rich dataset which we obtained for $^{50}$Ti. I will briefly point out similarities and differences between the fragmentation of neutron-adding strengths to excited states of even-$A$ $^{50}$Ti and odd-$A$ $^{51}$Ti, before I discuss $1^+$ and $1^-$ states of $^{50}$Ti populated in the $(d,p)$ reaction. By comparing to observables obtained from complementary experiments, I will make a case for how $(d,p)$ can be used to study the microscopic origin of the spin-flip $M1$ resonance [4] and of the low-energy $E1$ strength, often referred to as pygmy dipole resonance (PDR) [2,7].

The experimental program at the FSU John D. Fox Laboratory is supported by the U.S. National Science Foundation (PHY-2412808 and PHY-2405485) and by the U.S. National Nuclear Security Administration (DE-NA0004150) as part of CENTAUR. Support from Florida State University is gratefully acknowledged.

References:

1. M. Spieker and S. Almaraz-Calderon, Frontiers in Physics 12, 1511394 (2024).
2. M. Spieker, L. T. Baby, A. L. Conley, B. Kelly, M. Müscher, R. Renom, T. Schüttler, and A. Zilges, Phys. Rev. C
   108, 014311 (2023).
3. M. Spieker, L. A. Riley, M. Heinze, A. L. Conley, B. Kelly, P. D. Cottle, R. Aggarwal, S. Ajayi, L. T. Baby, S. Baker,
   I. Conroy, I. B. D’Amato, J. Esparza, S. Genty, I. Hay, K. W. Kemper, M. I. Khawaja, P. S. Kielb, A. N. Kuchera,
   E. Lopez-Saavedra, A. B. Morelock, J. Piekarewicz, A. Sandrik, V. Sitaraman, E. Temanson, C. Wibisono, and
   I. Wiedenhoever, Phys. Rev. C 112, 064331 (2025).
4. B. Kelly, M. Spieker, U. Friman-Gayer, L. T. Baby, T. Beck, A. L. Conley, S. W. Finch, J. Isaak, Krishichayan,
   E. Litvinova, H. Pai, N. Pietralla, D. Savran, W. Tornow, N. Tsoneva, A. Volya, and V. Werner, Phys. Rev. Lett.
   136, 082502 (2026).
5. A. Conley, B. Kelly, M. Spieker, R. Aggarwal, S. Ajayi, L. Baby, S. Baker, C. Benetti, I. Conroy, P. Cottle, I. D’Amato,
   P. DeRosa, J. Esparza, S. Genty, K. Hanselman, I. Hay, M. Heinze, D. Houlihan, M. Khawaja, P. Kielb, A. Kuchera,
   G. McCann, A. Morelock, E. Lopez-Saavedra, R. Renom, L. Riley, G. Ryan, A. Sandrik, V. Sitaraman, E. Temanson,
   M. Wheeler, C. Wibisono, and I. Wiedenhöver, Nuclear Instruments and Methods in Physics Research Section A:
   Accelerators, Spectrometers, Detectors and Associated Equipment 1058, 168827 (2024).
6. L. A. Riley, I. C. S. Hay, L. T. Baby, A. L. Conley, P. D. Cottle, J. Esparza, K. Hanselman, B. Kelly, K. W. Kemper,
   K. T. Macon, G. W. McCann, M. W. Quirin, R. Renom, R. L. Saunders, M. Spieker, and I. Wiedenhöver, Phys.
   Rev. C 106, 064308 (2022).
7. M. Spieker, Eur. Phys. J. A 61, 197 (2025).