More Like this

1. Reduction of spectroscopic overlap across the Z=8 shell in neutron-rich nuclei

   https://doi.org/10.1103/PhysRevC.109.054325  

   Redpath, T ; Guèye, P ; Baumann, T ; Brown, B A ; Cunningham, A ; DeYoung, P A ; Frank, N ; Hoffman, C R ; Kuchera, A N ; Godoy, B Monteagudo ; et al ( May 2024 , Physical Review C)

   Zhang, Lin (Ed.)

   The recent discovery and spectroscopic measurements of${}^{27}\mathrm{O}$and${}^{28}\mathrm{O}$suggests the disappearance of the$N=20$shell structure in these neutron-rich oxygen isotopes.

   We measured one- and two-proton removal cross sections from${}^{27}\mathrm{F}$and${}^{29}\mathrm{Ne}$, respectively, extracting spectroscopic factors and comparing them to shell model overlap functions coupled with eikonal reaction model calculations.

   The invariant mass technique was used to reconstruct the two-body (${}^{24}\mathrm{O}+n$) and three-body (${}^{24}\mathrm{O}+2n$) decay energies from knockout reactions of${}^{27}\mathrm{F}$(106.2 MeV/u) and${}^{29}\mathrm{Ne}$(112.8 MeV/u) beams impinging on a${}^9\mathrm{Be}$target.

   The one-proton removal from${}^{27}\mathrm{F}$strongly populated the ground state of${}^{26}\mathrm{O}$and the extracted cross section of$3.4_{-1.5}^{+0.3}$mb agrees with eikonal model calculations that are normalized by the shell model spectroscopic factors and account for the systematic reduction factor observed for single nucleon removal reactions within the models used. For the two-proton removal reaction from${}^{29}\mathrm{Ne}$an upper limit of 0.08 mb was extracted for populating states in${}^{27}\mathrm{O}$decaying though the ground state of${}^{26}\mathrm{O}$.

   The measured upper limit for the population of the ground state of${}^{26}\mathrm{O}$in the two-proton removal reaction from${}^{29}\mathrm{Ne}$indicates a significant difference in the underlying nuclear structure of${}^{27}\mathrm{F}$and${}^{29}\mathrm{Ne}$.

   Published by the American Physical Society2024 

   more » « less
2. Constraints on variation of the weak scale from big bang nucleosynthesis

   https://doi.org/10.1103/PhysRevD.109.123506  

   Burns, Anne-Katherine ; Keus, Venus ; Sher, Marc ; Tait, Tim_M P ( June 2024 , Physical Review D)

   Recently, the EMPRESS Collaboration has included new data in the extraction of the primordial${}^4\mathrm{He}$abundance from big bang nucleosynthesis (BBN), resulting in a determination that differs from the previous value and from theoretical expectations. There have been several studies attempting to explain this anomaly which involve variation of fundamental constants between the time of BBN and the present. Since the Higgs vacuum expectation value (vev) is the only dimensionful parameter in the Standard Model and it is already known to vary during the electroweak phase transition, we consider the possibility that the vev is slightly different during BBN compared to its present value. A modification of the vev changes not only particle masses but also affects, through mass thresholds, the QCD confinement scale. We use the recently developed yordial program to study this variation and its impact on the${}^4\mathrm{He}$and deuterium abundances. We find that bounds on$|\delta v/v|$are approximately 0.01, and that the EMPRESS result can be explained within$2\sigma$if$0.008<\delta v/v<0.02$, but at the cost of worsening the current$2\sigma$discrepancy in the deuterium abundance to over$3\sigma$.

   Published by the American Physical Society2024 

   more » « less
3. Measurement of the fraction of jet longitudinal momentum carried by Λc+ baryons in pp collisions

   https://doi.org/10.1103/PhysRevD.109.072005  

   Acharya, S ; Adamová, D ; Adler, A ; Aglieri_Rinella, G ; Agnello, M ; Agrawal, N ; Ahammed, Z ; Ahmad, S ; Ahn, S U ; Ahuja, I ; et al ( April 2024 , Physical Review D)

   Recent measurements of charm-baryon production in hadronic collisions have questioned the universality of charm-quark fragmentation across different collision systems. In this work the fragmentation of charm quarks into charm baryons is probed, by presenting the first measurement of the longitudinal jet momentum fraction carried by${\mathrm{\Lambda }}_c^{+}$baryons,$z_{\parallel }^{\mathrm{ch}}$, in hadronic collisions. The results are obtained in proton-proton ($pp$) collisions at$\sqrt{s}=13\mathrm{TeV}$at the LHC, with${\mathrm{\Lambda }}_c^{+}$baryons and charged (track-based) jets reconstructed in the transverse momentum intervals of$3\le p_T^{{\mathrm{\Lambda }}_c^{+}}<15\mathrm{GeV}/c$and$7\le p_T^{\text{jet ch}}<15\mathrm{GeV}/c$, respectively. The$z_{\parallel }^{\mathrm{ch}}$distribution is compared to a measurement of${\mathrm{D}}^0$-tagged charged jets in$pp$collisions as well as to 8 simulations. The data hints that the fragmentation of charm quarks into charm baryons is softer with respect to charm mesons, in the measured kinematic interval, as predicted by hadronization models which include color correlations beyond leading-color in the string formation.

   © 2024 CERN, for the ALICE Collaboration2024CERN 

   more » « less
4. Search for prompt production of pentaquarks in charm hadron final states

   https://doi.org/10.1103/PhysRevD.110.032001  

   Aaij, R ; Abdelmotteleb, A_S W ; Abellan_Beteta, C ; Abudinén, F ; Ackernley, T ; Adeva, B ; Adinolfi, M ; Adlarson, P ; Afsharnia, H ; Agapopoulou, C ; et al ( August 2024 , Physical Review D)

   A search for hidden-charm pentaquark states decaying to a range of${\mathrm{\Sigma }}_c\overline{D}$and${\mathrm{\Lambda }}_c^{+}\overline{D}$final states, as well as doubly charmed pentaquark states to${\mathrm{\Sigma }}_{c}D$and${\mathrm{\Lambda }}_c^{+}D$, is made using samples of proton-proton collision data corresponding to an integrated luminosity of$5.7{\mathrm{fb}}^{-1}$recorded by the LHCb detector at$\sqrt{s}=13\mathrm{TeV}$. Since no significant signals are found, upper limits are set on the pentaquark yields relative to that of the${\mathrm{\Lambda }}_c^{+}$baryon in the${\mathrm{\Lambda }}_c^{+}\to p{K}^{-}{\pi }^{+}$decay mode. The known pentaquark states are also investigated, and their signal yields are found to be consistent with zero in all cases.

   © 2024 CERN, for the LHCb Collaboration2024CERN 

   more » « less
5. Effective field theory and inelastic dark matter results from XENON1T

   https://doi.org/10.1103/PhysRevD.109.112017  

   Aprile, E ; Abe, K ; Agostini, F ; Ahmed_Maouloud, S ; Althueser, L ; Andrieu, B ; Angelino, E ; Angevaare, J R ; Antochi, V C ; Antón_Martin, D ; et al ( June 2024 , Physical Review D)

   In this work, we expand on the XENON1T nuclear recoil searches to study the individual signals of dark matter interactions from operators up to dimension eight in a chiral effective field theory (ChEFT) and a model of inelastic dark matter (iDM). We analyze data from two science runs of the XENON1T detector totaling$1\mathrm{t}\times \mathrm{yr}$exposure. For these analyses, we extended the region of interest from$[4.9,40.9]{\mathrm{keV}}_{\mathrm{NR}}$to$[4.9,54.4]{\mathrm{keV}}_{\mathrm{NR}}$to enhance our sensitivity for signals that peak at nonzero energies. We show that the data are consistent with the background-only hypothesis, with a small background overfluctuation observed peaking between 20 and$50{\mathrm{keV}}_{\mathrm{NR}}$, resulting in a maximum local discovery significance of$1.7\sigma$for the$\mathrm{Vector}\otimes {\text{Vector}}_{\text{strange}}$ChEFT channel for a dark matter particle of$70\mathrm{GeV}/c^2$and$1.8\sigma$for an iDM particle of$50\mathrm{GeV}/c^2$with a mass splitting of$100\mathrm{keV}/c^2$. For each model, we report 90% confidence level upper limits. We also report upper limits on three benchmark models of dark matter interaction using ChEFT where we investigate the effect of isospin-breaking interactions. We observe rate-driven cancellations in regions of the isospin-breaking couplings, leading to up to 6 orders of magnitude weaker upper limits with respect to the isospin-conserving case.

   Published by the American Physical Society2024 

   more » « less