{"id":"dc7da670-db47-4a10-aaab-884b4cd4c81f","arxiv_id":"2411.09835","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":6.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":1,"one_line_summary":"The first inclusive and partial proton-removal cross sections for 72,74Se from 73,75Br beams are reported; total yields are equal within uncertainties and excited-state fragmentation is mapped.","lead":"Physicists measured how often proton removal from two radioactive bromine isotopes produces excited states of selenium isotopes, finding nearly equal total cross sections for both. The new data map which proton orbits are occupied in a region known for rapid changes in nuclear shape.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"The 73Br beam may contain an unresolved 26.9-keV isomer; if so the 72Se partial cross sections and the orbital/multi-step interpretation rest on an unquantified beam admixture.","rationale":"The paper is a careful experimental report. The inclusive cross sections, 68(4) and 66(4) mb, and the partial cross-section tables appear to be the primary data contribution, derived from a standard GRETINA+S800 analysis with geant4 simulations; I do not find an arithmetic or procedural error to point to. The central interpretive claims are explicitly hedged with language such as 'might suggest', 'could', and 'seems to indicate', and the authors themselves call for dedicated structure and reaction calculations. My concern is not that the measured cross sections are wrong, but that one unquantified experimental condition, the possible 5/2^- isomeric component in the 73Br beam, sits underneath the comparison of proton removal from 73Br and 75Br. The paper estimates that the 26.9-keV state lifetime could be about 800 ns, long enough to survive to the target, and then argues the effect is minor because the two selenium isotopes show similar partial-cross-section patterns. That argument does not close the issue: different final nuclei can have similar inclusive cross sections for different reasons, and a 5/2^- component would naturally explain the observed 6+ population without invoking multi-step processes. The reader's weakest assumption, transferability of (d,3He) spectroscopic factors, is related but downstream: even if those spectroscopic factors transfer perfectly, an isomeric admixture changes the initial state from which the removal occurs. For this reason I regard the isomer issue as the most load-bearing. A lifetime measurement is a single, well-defined check. If the lifetime turns out to be short, the concern is retired and the paper stands as a solid data report with provisional interpretation. If it is long, the equal-cross-section and multi-step conclusions need to be revised or conditioned on isomeric tagging. This leaves the reader's CONDITIONAL verdict essentially unchanged but sharpens the condition that should be attached to the interpretation.","tokens_in":20257,"tokens_out":5458,"duration_ms":57548,"concrete_test":"Measure the half-life of the 26.9-keV state in 73Br, for example by fast-timing of conversion electrons or with LaBr3(Ce) detectors following implantation or decay, or measure the isomeric fraction in the A1900/S800 beam using time-dependent gamma-ray tagging. If the lifetime is about 100 ns or less, the isomer has decayed before the target and the concern is retired. If the lifetime is about 300 ns or longer, the data must be reanalyzed with the 5/2^- component included, and the equal-cross-section and multi-step interpretations should be treated as not established without isomeric tagging.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The most load-bearing unresolved issue is the possible isomeric component of the 73Br secondary beam. The paper itself notes (Section III) that 73Br has a 26.9-keV state of unknown lifetime and that, assuming a B(E2) as in 71Se, the lifetime could be about 800 ns. At v/c about 0.4 over the flight path from production to the LH2 target, a substantial fraction of such an isomer would survive to the reaction point. The inclusive cross section for 73Br(p,2p)72Se would then be a weighted average of proton removal from the J^pi = 1/2^- ground state and the 5/2^- isomer, and the measured partial cross sections to the 6+ and 8+ states could be direct knockout from the 5/2^- component rather than evidence for multi-step processes. The authors argue that the similarity of the 72Se and 74Se patterns implies the isomer effect is minor, but this is indirect because the final nuclei differ; similar inclusive cross sections do not constrain the initial-state admixture. Since 75Br has no such low-lying isomer, the equality of the inclusive cross sections could be fortuitous. This does not invalidate the measured inclusive and partial cross sections as data for the delivered beam, but it does undercut the orbital-equality and multi-step conclusions unless the isomeric fraction is quantified.","agreement_with_reader":"partial"},"referee_report":{"model":"deepseek-v4-flash","summary":"The manuscript reports inclusive and partial cross sections for proton removal from 73Br and 75Br on a liquid-hydrogen target, populating 72Se and 74Se at mid-target energies of about 95 and 89 MeV/u, respectively. Inclusive cross sections of 68(4) mb and 66(4) mb are measured and agree within uncertainties. Using GRETINA and the S800 spectrograph, partial cross sections for resolved excited states are extracted from Doppler-corrected gamma-ray spectra via UCGRETINA/GEANT4 simulations, including corrections for observed feeding. The data are compared with the earlier 9Be(71Br,X)70Se measurement of Wimmer et al. The paper suggests, with explicit hedging, that the similarity of the inclusive cross sections and partial-cross-section patterns might indicate the same proton orbitals (fp, sd, 1g9/2) contribute, that a comparison with (d,3He) data on stable Ge/Se targets suggests a lower-energy concentration of l=1-4 strength in Se than in Ge, and that population of high-spin states (6+, 8+, 7-) may indicate multi-step processes. The authors call for dedicated structure and reaction calculations and note limitations, including possible isomeric contamination.","tokens_in":20524,"tokens_out":7432,"duration_ms":76246,"significance":"If the measured cross sections stand, the data are a useful addition to the sparse proton-removal systematics in the neutron-deficient Ge-Se region: they provide the first partial cross sections for excited states of 72,74Se and extend the comparison to the N=36 case. The experimental analysis is careful: event-by-event particle identification, standard gamma-ray tracking simulations with known branching ratios, and stated uncertainty contributions including target thickness, beam composition, and software gating. The manuscript is appropriately hedged in most interpretive statements. The main scientific value lies in the data themselves and in the qualitative comparison with normal-kinematics transfer; the interpretive claims about identical orbital content and multi-step mechanisms are suggestive rather than established.","major_comments":[{"comment":"The possible 26.9-keV isomeric component of the 73Br beam is not quantified, and the argument given for dismissing it is indirect. The paper estimates an approximately 800 ns lifetime from the 71Se B(E2) value; at v/c about 0.4, such a state can survive to the reaction target in a substantial fraction of the beam. If a fraction of the beam is in the 5/2- isomer, the inclusive cross section and every partial cross section in Table I are weighted averages over two initial states. In particular, the populations of the 6+1 and 8+1 states could be direct knockout from the 5/2- isomer rather than evidence for multi-step processes. The paper's counterargument, that the 72Se and 74Se patterns are similar and that 75Br has no such low-lying isomer, does not constrain the 73Br admixture, because the final nuclei and the ground-state spins differ. Since the orbital-equality and multi-step conclusions depend on this point, the manuscript should either provide a quantitative estimate of the isomeric fraction (or an upper limit from the data) and its effect on the partial cross sections, or explicitly state that these interpretations are contingent on an unresolved systematic uncertainty. A concrete test would be to compute the isomeric fraction needed to reproduce the observed 6+1 cross section and compare it with the beam composition implied by the production and transport times.","section":"Section III, first paragraph and abstract"},{"comment":"The assignment of l=1,2,3,4 contributions and the claim that the spectroscopic strength lies lower in Se than in Ge rest on transferring spectroscopic factors from the 75As(d,3He)74Ge and 72Ge/74Se(d,3He) reactions at Ed=26 MeV (Refs. [69-71]) to intermediate-energy proton removal from 73,75Br beams. These are different reactions (normal kinematics, stable targets, different Q-values and distortions) and different initial nuclei (1/2- and 3/2- Br ground states versus 3/2- As and 0+ Ge/Se targets). The comparison is qualitative, and the authors acknowledge that firm conclusions require dedicated calculations. The abstract, however, states that the available data 'suggest indeed' that fp, sd, and 1g9/2 contribute. I recommend either including eikonal-plus-shell-model calculations for 73,75Br(p,2p), which the authors state are challenging but appear within reach given the schematic calculations mentioned in the acknowledgments, or rewording the abstract and conclusions so that the (d,3He) comparison is explicitly a qualitative benchmark rather than a quantitative transfer of spectroscopic factors.","section":"Section III, first paragraph and abstract"},{"comment":"The inference from equality of inclusive cross sections to 'the same single-particle orbitals contribute' is not logically forced: many different orbital mixtures can produce the same inclusive cross section, especially once the isomeric admixture and reaction-theory uncertainties are considered. The manuscript later says that this statement cannot be backed up without calculations, but the abstract and the opening of Section III present it as a suggestion without the same caveat. The abstract should be tempered to 'consistent with' rather than 'suggesting that the same orbitals contribute,' or the caveat should appear in the abstract.","section":"Section III, first paragraph and abstract"}],"minor_comments":[{"comment":"The unplaced 2537-keV and 2900-keV transitions are assigned partial cross sections of 2.0(7) and 1.1(6) mb, but these values depend on their unobserved decay paths; please state explicitly that these are transition yields, not final-state partial cross sections, and give an upper limit on any direct ground-state feeding.","section":null},{"comment":"The text says that 'no specific trend can be claimed' but then describes possible trends; I suggest moving the trend discussion to a clearly labeled speculative paragraph, or adding a sentence that these trends are not significant at the present precision.","section":null},{"comment":"The paper does not give the time of flight from the production target to the LH2 target; for the 73Br isomer discussion, this time is essential, so please state the distance or time and explicitly estimate the surviving fraction of a state with an 800 ns lifetime.","section":null},{"comment":"The abstract says the inclusive cross sections are 'identical'; the quantitative statement in Section III is that they 'agree within uncertainties,' which is more precise and should be used in the abstract.","section":null},{"comment":"The summation symbol in 'P σpart. = 51(7) mb' appears to be a rendering error for the capital sigma; please correct the typography.","section":null}],"recommendation":"major_revision","confidential_remarks":"The paper is a measurement paper with a clear experimental result. The main risk is the unresolved isomeric component of 73Br; if the authors can provide a sensitivity estimate or an upper limit on the isomeric fraction, the interpretive claims could be made robust. The comparison with (d,3He) data is qualitative, and I would ask that the abstract be aligned with the caveats already present in the text. The paper is within the scope of a nucl-ex journal such as Physical Review C."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"The story here is the new data: first proton-removal cross sections for 72,74Se, inclusive 68(4) and 66(4) mb, plus partial cross sections to excited states. That is a solid extension of Wimmer's 70Se work. The analysis follows the standard GRETINA+S800 and ucgretina fitting procedure, and the uncertainties include target thickness and beam composition. The paper is honest about its limits: it explicitly calls for eikonal plus shell-model calculations rather than claiming to have them.\n\nThe soft spots are real but not disqualifying. The 73Br beam may contain a 26.9-keV 5/2^- isomer with unknown lifetime. The authors flag this, estimate ~800 ns from an assumed B(E2), and argue that the similarity of the 72Se and 74Se patterns makes the effect minor. That argument is indirect: 75Br has no such isomer, so equal inclusive cross sections do not by themselves constrain the 73Br admixture. If a sizable fraction of the beam is the isomer, the high-J (6+, 8+) partial cross sections in 72Se could be direct knockout from the 5/2^- state rather than evidence for multi-step processes. The authors acknowledge this possibility but do not quantify it. This weakens the orbital-equality and multi-step interpretations, not the measured cross sections for the delivered beam.\n\nThe other caveat is the use of (d,3He) spectroscopic factors from stable Ge/Se targets to interpret proton removal from neutron-deficient Br beams. That transferability is assumed, not established, and the authors are explicit about it. The two unplaced transitions in 74Se are a minor issue.\n\nBottom line: this is a careful experimental report with new data that will be useful benchmarks for structure and reaction codes in a shape-transitional region. It does not overclaim. It deserves a serious referee. I would ask the referee to request a more quantitative statement about the isomeric fraction, or a limit, and a clearer separation of measured cross sections from tentative interpretation.","headline":"New inclusive and partial proton-removal cross sections for 72,74Se that look solid, with an unquantified 73Br isomer as the main caveat.","tokens_in":21098,"tokens_out":3681,"would_cite":true,"duration_ms":36491,"reading_group":"maybe","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"deepseek-v4-flash","headline":"Proton removal from 73Br and 75Br on a proton target gives equal inclusive cross sections into 72Se and 74Se, hinting that the same proton orbitals drive both reactions.","keywords":["proton removal","intermediate-energy knockout","inclusive cross sections","partial cross sections","72Se","74Se","single-particle orbitals","multi-step reaction processes"],"falsifier":"Measure the longitudinal momentum distributions of the 72Se and 74Se residues tagged by their decay gamma rays. If the momentum distribution shapes for corresponding final states differ significantly between the two reactions, the single-particle orbital content is not the same, contradicting the equal-orbital interpretation. The same measurement could also reveal whether the high-spin states carry a different momentum signature than the low-spin states, testing the multi-step hypothesis.","tokens_in":20073,"feed_emoji":"⚛️","tokens_out":10979,"duration_ms":98406,"temperature":0.7,"pith_summary":"The paper reports the first proton-removal measurements on a liquid-hydrogen target for the short-lived nuclei 73Br and 75Br, populating 72Se and 74Se. The central data result is that the inclusive cross sections, 68(4) mb and 66(4) mb, are identical within uncertainties, which would follow naturally if the same proton single-particle orbitals are occupied in both bromine isotopes. Using the GRETINA gamma-ray array, the authors resolve partial cross sections to many excited states and find a similar fragmentation pattern in both selenium isotopes. Comparing with older (d,3He) transfer data on stable germanium and selenium targets, they argue that fp-shell, sd-shell, and 1g9/2 orbitals all contribute and that the proton spectroscopic strength sits at lower excitation energy in selenium than in germanium. The paper also notes the population of high-spin states (up to 8+ in 72Se and 7- in 74Se) as evidence that multi-step reaction processes play a role at intermediate energies.","feed_headline":"73,75Br proton removal yields equal cross sections into 72,74Se","feed_subtitle":"Matching cross sections into 72Se and 74Se suggest the same proton orbitals drive both reactions.","key_machinery":"The central tool is the proton-removal reaction in inverse kinematics on a liquid-hydrogen target, measured with the S800 spectrograph for inclusive cross sections and with the GRETINA gamma-ray tracking array for gamma-tagged partial cross sections. The argument that the same orbitals are involved rests on the ratio of partial to inclusive cross sections and on a comparison of the measured partial cross sections with spectroscopic factors from (d,3He) transfer reactions on stable germanium and selenium targets, which decompose the strength into l=1, 2, 3, and 4 transfers. This comparison is the mechanism that connects the knockout data to specific single-particle orbitals.","core_discovery":"The paper establishes the inclusive and partial cross sections for proton removal from 73Br and 75Br on a proton target, 72Se and 74Se being the residues. The inclusive cross sections, 68(4) mb and 66(4) mb, agree within uncertainties, and the partial cross sections for resolved excited states show closely similar magnitudes and fragmentation in the two isotopes. From a comparison with (d,3He) data on stable targets, the authors tentatively conclude that angular-momentum transfers l=1, 2, 3, and 4 (the fp shell, the sd shell, and the 1g9/2 orbital) all contribute, and that the bulk of this strength appears at lower excitation energies in the selenium isotopes than in the germanium isotopes. The observed population of high-spin states—6+ in both isotopes, 7- in 74Se, and 8+ in 72Se—from projectiles with known low ground-state spins suggests that multi-step processes contribute to the reaction, an effect outside current eikonal reaction theory. The authors are explicit that these orbital and multi-step conclusions require dedicated structure and reaction calculations to be confirmed.","pith_inferences":["A decisive test of the 'same orbitals' claim is to measure the longitudinal momentum distributions of the residues: matching final states should have similar momentum shapes if the orbital content is identical.","If multi-step processes are confirmed, inclusive proton-removal cross sections alone should not be used to extract spectroscopic factors in deformed nuclei; partial cross sections and momentum distributions carry the needed information.","The equal-cross-section result may hold for other isotope pairs in the same region; checking, for instance, proton removal from neighboring rubidium or krypton isotopes would show whether the pattern is general.","A dedicated measurement of the lifetime of the 27-keV state in 73Br would remove the one beam-contamination caveat the authors could not fully exclude."],"forward_implications":["If the equal inclusive cross sections reflect the same orbital occupancies, then the different ground-state spins of 73Br (1/2-) and 75Br (3/2-) do not significantly alter the total proton-removal strength.","If the l=1-4 strength is indeed concentrated at lower excitation energy in selenium than in germanium, then the proton single-particle structure follows the shape-transitional behavior in this mass region and could be connected to the enhanced octupole collectivity near A=72.","If multi-step processes contribute as the high-spin populations suggest, eikonal reaction theory would need to be extended to extract reliable spectroscopic factors from these reactions in collective nuclei.","The new partial cross sections for 72,74Se extend the 70Se data to a three-isotope chain, providing a testing ground for shell-model and beyond-mean-field predictions of proton occupancies."],"supporting_citations":[{"why":"Provides the 70Se data point from proton knockout on a beryllium target, the third isotope in the comparison chain.","marker":"[15]"},{"why":"The geant4-based simulation used to fit gamma-ray spectra and correct yields for feeding; central to all partial cross sections.","marker":"[59]"},{"why":"Establishes the liquid-hydrogen target thickness from energy-loss distributions; required for the absolute inclusive cross sections.","marker":"[64]"},{"why":"Adopted level energies, spin-parities, and gamma branching ratios used to assign and simulate the decays of 72,74Se.","marker":"[65]"},{"why":"The 75As(d,3He)74Ge transfer measurement that supplies the l=1-4 spectroscopic strengths used to interpret the proton-removal pattern.","marker":"[69]"},{"why":"(d,3He) data on germanium targets showing the location of l=2,4 strength in that chain, the baseline for the energy-shift comparison.","marker":"[70]"},{"why":"(d,3He) data on selenium targets that place l=2,4 (and l=1,3) strength lower in excitation energy, supporting the selenium-versus-germanium shift.","marker":"[71]"},{"why":"Reaction-theory study of multi-step contributions that the authors cite as a framework for interpreting the high-spin population.","marker":"[72]"}],"fun_headline_variants":["73,75Br proton removal yields equal Se cross sections","Equal proton-removal cross sections from 73,75Br to Se","High-spin states hint multi-step effects in proton removal","Proton removal hints at shared orbitals in Se isotopes"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The orbital and energy-shift conclusions depend on the assumption that spectroscopic factors from (d,3He) transfer reactions on stable germanium and selenium targets can be transferred to intermediate-energy proton removal from the short-lived bromine beams; if this transferability fails, those interpretations collapse even though the measured cross sections would still stand.","fun_headline_variants_meta":{"raw":{"variants":["73,75Br proton removal yields equal Se cross sections","Equal proton-removal cross sections from 73,75Br to Se","High-spin states hint multi-step effects in proton removal","Proton removal hints at shared orbitals in Se isotopes"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000829,"raw_usage":{"total_tokens":3693,"prompt_tokens":1090,"completion_tokens":2603,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":706,"completion_tokens_details":{"reasoning_tokens":2533}},"tokens_in":706,"tokens_out":2603,"duration_ms":18813,"temperature":1.0,"reasoning_tokens":2533,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-12T20:15:34.731079+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Measure the longitudinal momentum distributions of the 72Se and 74Se residues tagged by their decay gamma rays. If the momentum distribution shapes for corresponding final states differ significantly between the two reactions, the single-particle orbital content is not the same, contradicting the equal-orbital interpretation. The same measurement could also reveal whether the high-spin states carry a different momentum signature than the low-spin states, testing the multi-step hypothesis.","supporting_citations":[{"cited_title":"Wimmer, W","cited_arxiv_id":null,"evidence_quote":"Provides the 70Se data point from proton knockout on a beryllium target, the third isotope in the comparison chain."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"The geant4-based simulation used to fit gamma-ray spectra and correct yields for feeding; central to all partial cross sections."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Establishes the liquid-hydrogen target thickness from energy-loss distributions; required for the absolute inclusive cross sections."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Adopted level energies, spin-parities, and gamma branching ratios used to assign and simulate the decays of 72,74Se."},{"cited_title":"Rotbard, M","cited_arxiv_id":null,"evidence_quote":"The 75As(d,3He)74Ge transfer measurement that supplies the l=1-4 spectroscopic strengths used to interpret the proton-removal pattern."},{"cited_title":"Rotbard, G","cited_arxiv_id":null,"evidence_quote":"(d,3He) data on germanium targets showing the location of l=2,4 strength in that chain, the baseline for the energy-shift comparison."},{"cited_title":"Rotbard, M","cited_arxiv_id":null,"evidence_quote":"(d,3He) data on selenium targets that place l=2,4 (and l=1,3) strength lower in excitation energy, supporting the selenium-versus-germanium shift."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Reaction-theory study of multi-step contributions that the authors cite as a framework for interpreting the high-spin population."}],"review_version":1}