From outer space to deep inside: exploring neutron skins of nuclei

Transcription

1 From outer space to deep inside: exploring neutron skins of nuclei

2 Neutron in for beginner Nuclear charge radii Where do the neutrons go?

3 Neutron in for beginner Where do the neutrons go? Pressure forces neutrons out against surface tension EOS

4 18-OM smaller 55-OM lighter same EOS symmetry energy

5 18-OM smaller 55-OM lighter same EOS symmetry energy slope parameter curvature parameter

6 18-OM smaller 55-OM lighter same EOS symmetry energy slope parameter curvature parameter

7 18-OM smaller 55-OM lighter same EOS symmetry energy X. Roca-Maza, at al. Phys. Rev. Lett. 106, (2011) slope parameter 0.3 Linear Fit, r = Nonrelativistic models Relativistic models NL3* NL3 PK1 NL-SV2 TM1 NL2 NL1 r np (fm) X -T6 HFB-17 M* FSUGold DD-ME1 DD-ME2 MP SM* SIV MSL0 MA a DD-PC1 PK1.s24 -T4 NL3.s25 -Rs RHF-PKO3 G2 I2 RHF-PKA1 SV -Gs I5 G1 NL-RA1 PC-F1 NL-SH PC-PK1 curvature parameter 0.15 HFB-8 M7 v090 P SGII D1N SLy5 SLy4 BCP D1S L (MeV)

8 from deep inside to outer space Neutron skins constrain the EOS ρ] PREX/JLAB M. B. Tsang PRC (2012) low ρ Crust thickness

9 The answer to the ultimate question What do these data points have in common?

10 The answer to the ultimate question What do these data points have in common? NONE of the experiments measured neutron skin!!!

11 ...do we produce these plots in the first place?!?! WHY? PHYSICAL REVIEW C88, (2013) SV-min FSUGold PREX Ca F w (q) Pb F w 10 qcrex q(fm -1 )

12 Uncontrolled Uncertainties ximatio WHAT? ISI + FSI (syst)theo??

13 Uncontrolled Uncertainties ximatio WHAT? (syst)theo??

14 WHAT? Resonances

15 Dipole Polarizability Enormous progress in sight y of nuclei at RCNP & GS WHAT? Resonances A. Tamii et al., Phys. Rev. Lett. 107, (2001)

16 The long winding road......from measurable observables to the neutron skin CAUTION NEUTRON SKIN AHEAD All observables are equal, but some observables are more equal than others Pedigree! Neutron ins of Nuclei: from laboratory to stars C. Horowitz, J. Piekarewicz, CS, MVdH

17 The long winding road......from measurable observables to the neutron skin observables, How is the measured observable connected to the neutron skin? What are the assumptions implicit in making this connection? Impulse approximation, off-shell ambiguities, distortion effects, How sensitive is the extraction of What is actually measured? Cross section, asymmetry, spin observables, How is the measured observable ambiguities, distortion effects, How sensitive is the extraction of the neutron radius/skin to these assumptions? Quantitative assessment of both statistical and systematic errors Neutron ins of Nuclei: from laboratory to stars C. Horowitz, J. Piekarewicz, CS, MVdH

18 Theory informing experiment Theory Informing Experiment Quantitative assessment of both statistical and systematic errors; theory must provide error bars! Uncertainty quantification and covariance analysis (theoretical errors & correlations) Precision required in the determination of the neutron radius/skin? CAUTION NEUTRON SKIN AHEAD As precisely as humanly possible - fundamental nuclear structure property To strongly impact Astrophysics? Quantitative assessment of both statistical What astrophysical observables to and systematic errors; theory must benchmark? provide error bars! Uncertainty Is there quantification a need for and a systematic covariance analysis study (theoretical over many errors & nuclei? correlations) PREX, CREX, SREX, ZREX, Is there a need for more than one Q-square point? Radius and diffuseness the whole form factor? 10 0 observables to the 10-1 F c (q) R ch =5.5012(13) fm...from measurable neutron skin (theoretical errors r skin & =0.260 correlations) fm 10-4 Exp. r skin =0.176 fm r skin =0.207 fm r skin =0.235 fm r skin =0.286 fm Precision 0.0 required 0.5 in 1.0the determination of the q (fm neutron radius/skin? -1 ) As precisely R as humanly possible - fundamental wk =5.826(181) fm nuclear structure property 10 To strongly 0 impact Astrophysics? PREX r What astrophysical observables skin =0.176 fm to benchmark? F weak (q) 10-1 Is there a need for a systematic study 10 over many -2 nuclei? PREX, CREX, SREX, ZREX, 10-3 r skin =0.207 fm r skin =0.235 fm r skin =0.260 fm r skin =0.286 fm Neutron ins of Nuclei: from laboratory to stars q (fm -1 ) C. Horowitz, J. Piekarewicz, CS, MVdH

19 MESA: Parity Violation Neutron

20 PVES Enormously Clean Extraordinarily Expensive!

21 ctroweak Measurements ken mirror 2" 47 AA Groningen, The Enormously Clean Expensive! t method: e- scattering PVES PVExtraordinarily um, further aiding t complement ongoing 2" Weak FF determined in a model independent way (exactly as the 2" Charge FF) n: Carin Cain ic force via the eak e!ects by... Show ring ak force, which very ts the ground state of an interaction between the!orts is required to te. Tsigutkin et al.s hains ate theory Very strongly coupled to nin Mild model dependence going from FF to nin (Theory Homework) 2" Measuring the FF at two (or more) points (Experiment/Theory Homework) Measuring the FF in several nuclei? (Experiment/Theory Homework) Understanding dispersive corrections (Theory Homework) 5/12 Full azimuthal coverage 4xstat

22 ctroweak Measurements ken mirror 2" 47 AA Groningen, The Enormously Clean Expensive! t method: e- scattering PVES PVExtraordinarily um, further aiding t complement ongoing 2" Weak FF determined in a model independent way (exactly as the 2" Charge FF) n: Carin Cain ic force via the eak e!ects by... Show ring ak force, which very ts the ground state of an interaction between the!orts is required to Very strongly coupled to nin Mild model dependence going from FF to nin (Theory Homework) te. Tsigutkin et al.s hains ate theory 2" Measuring the FF at two (or more) points (Experiment/Theory Homework) Measuring the FF in several nuclei? (Experiment/Theory Homework) Understanding dispersive corrections (Theory Homework) SensiQvity 5/12 Full azimuthal coverage 4xstat Uncertainty Assuming same PREX luminosity: Δθ=4o : Rate=8.25 GHz, APV=0.66 ppm 1440h δrn/rn = 0.5% (assuming 1% syst. δapv/apv)

23 1 st possibility: 208 Pb

24 1 st possibility: 208 Pb 2 nd possibility: 48 Ca G. Hagen et al., Nature Physics 12, (2016)

25 C. J. Horowitz, Phys. Rev. C 92, (2015) 1 st possibility: 208 Pb 2 nd possibility: 48 Ca 3 rd possibility: more Q 2 points Stat. Error 2 months beam Qme

26 The long winding road... Is there a need for a systematic study over many nuclei? PREX, CREX, SREX, ZREX, S (fm) M. Centelles, et al Phys. Rev. Lett. 102, (2009) experiment Cd Zr 50 Sn 52 Te 48 Cd 50 Sn Te 90 Th linear average of experiment prediction Eq. (2) FSUGold SLy Fe Ca Ni Fe 28 Ni 56 Fe Co Sn Ni Te Te Te Zr Ca Sn I = (N Ζ) / Α Bi Pb U

27 The long winding road... Is there a need for a systematic study over many nuclei? PREX, CREX, SREX, ZREX, S (fm) M. Centelles, et al Phys. Rev. Lett. 102, (2009) experiment Cd Zr 50 Sn 52 Te 48 Cd 50 Sn Te 90 Th linear average of experiment prediction Eq. (2) FSUGold SLy Fe Ca Ni Fe 28 Ni 56 Fe Co Sn Ni Te Te Te Zr Ca Sn I = (N Ζ) / Α Bi Pb U if (YES) { if (MONEY== && TIME == ){ (PVES) } else { (INDIRECT METHOD)} }

28 The long winding road... Is there a need for a systematic study over many nuclei? PREX, CREX, SREX, ZREX, S (fm) M. Centelles, et al Phys. Rev. Lett. 102, (2009) experiment Cd Zr 50 Sn 52 Te 48 Cd 50 Sn Te 90 Th linear average of experiment prediction Eq. (2) FSUGold SLy Fe Ca Ni Fe 28 Ni 56 Fe Co Sn Ni Te Te Te Zr Ca Sn I = (N Ζ) / Α Bi Pb U if (YES) { if (MONEY== && TIME == ){ (PVES) } else { (INDIRECT METHOD)} } Neutron skin extraction: Nuclear structure away from stability Experiment informing theory

29 Neutron MAGIX: Internal Target Polarizability: Compton scattering LYSO detector and Si-Recoil detector

30 Neutron MAGIX: Internal Target Polarizability: Compton scattering LYSO detector and Si-Recoil detector BBN program

31 Pb Radius Neutron Radius From outer vs space to deepstar inside: exploring neutron skins of nuclei The 208Pb radius constrains the PHYSICAL REVIEW LETTERS 6, (2011) of neutron pressure matter at Equation Of State 1 NL subnuclear densities. Typel + Brown between P at I5 2 NL 1 G1 -RA NL -F1 3* NL 3 PCL-SH 1 N -PK NLK1 PC P V2 1 -S KA I2 NL TM1 F-P RH SV s G2 G 3 -T4 KO F-P 25 RH 3.s -Rs NL 24 1.s MP a M* PK 1 S -PC DD SIVSL0 A M M P old UG BC FS E1 -M y5 SL y4 DD -ME2 SL DD M* Linear Fit, r = find sharp correlation Nonrelativistic models Relativistic models 2/3 ρ0 and Rn. P 7 B-1 HFX 6 -T The NS radius depends on the pressure at nuclear density and above. Central density of NS few to 10 x nuclear density. Pb radius probes low density, NS radius medium density, and maximum NS mass probes high density equation of state. An observed softening of EOS with L (MeV)increase in pressure) density (smaller could Neutron stronglyskin suggest a transition (color online). of 208 Pb against slopeto exotic high density phase as ¼such 0:101 þ symmetryanenergy. The linear fit is!r np slope parameter quark or ain L. A sample testmatter, constraintstrange from a matter, 3% accuracy rawn. color superconductor II SG N D1 D1 B-8 HF k7 MS 0 9 v0 S J. Piekarewicz, CJH t. Then, we have to conclude that a 3% accuracy in s modest constraints on L, implying that some of ectations that this measurement will constrain L y may have to be revised to some extent. To narrow L, though demanding more experimental effort, a measurement of APV should be sought ultimately in Our approach can support it to yield a new accuracy!rnp! 0:02 fm and!l! 10 MeV, well below any s constraint. Moreover, PREX is unique in that the value of!rnp and L follows from a probe largely strong force uncertainties. mmary, PREX ought to be instrumental to pave the r electroweak studies of neutron densities in heavy [9,10,26]. To accurately extract the neutron radius n of 208 Pb from the experiment requires a precise ion between the parity-violating asymmetry APV se properties. We investigated parity-violating elecattering in nuclear models constrained by available ory data to support this extraction without specific tions on the shape of the nucleon densities. We trated a linear correlation, universal in the mean mework, between APV and!rnp that has very small Because of its high quality, it will not spoil the mental accuracy even in improved measurements of ith a 1% measurement of APV it can allow one to in the slope L of the symmetry energy to near a 0 MeV level. A mostly model-independent detern of!rnp of 208 Pb and L should have enduring on a variety of fields, including atomic parity servation and low-energy tests of the standard [8,9,32]. hank G. Colo, A. Polls, P. Schuck, and E. Vives uable discussions, H. Liang for the densities of F-PK and PC-PK models, and K. Kumar for inforon PREX kinematics. Work supported by the der Ingenio Programme CPAN CSD curvature parameter week ending 24 JUNE 2011 and Grants No. FIS from MEC and FEDER, No. 2009SGR-1289 from Generalitat de Catalunya, and No. N N from Polish MNiSW. The Good [1] Special issue on The Fifth International Conference on Exotic Nuclei and Atomic Masses ENAM 08, edited by M. Pfu tzner [Eur. Phys. J. A 42, 299 (2009)]. [2] G. W. Hoffmann et al., Phys. Rev. C 21, 1488 (1980). [3] J. Zenihiro et al., Phys. Rev. C 82, (2010). [4] A. Krasznahorkay et al., Nucl. Phys. A731, 224 (2004). [5] B. Kłos et al., Phys. Rev. C 76, (2007). [6] E. Friedman, Hyperfine Interact. 193, 33 (2009). [7] T. W. Donnelly, J. Dubach, and Ingo Sick, Nucl. Phys. Chiral EFT calc. of pressure P of neutron A503, 589 (1989). matter by et Hebeler al.cincluding [8] D. Vretenar al., Phys.et Rev. 61, three (2000). [9] neutron C. J. Horowitz, J. Pollock, P. A. Souder, forces S. (blue band) agree with and R. Michaels, Phys. Rev. 63, (2001). PREX results but Ctwo nucleon only [10] K. Kumar, P. A. Souder, R. Michaels, and G. M. Urciuoli, calculations yield smaller P. (see section Status and Plans for latest updates). [11] M. Centelles, X. Roca-Maza, X. Vin as, and M. Warda, Phys. Rev. C 82, (2010). [12] I. Angeli, At. Data Nucl. Data Tables 87, 185 (2004). [13] B. A. Brown, Phys. Rev. Lett. 85, 5296 (2000); S. Typel and B. A. Brown, Phys. Rev. C 64, (2001). [14] R. J. Furnstahl, Nucl. Phys. A706, 85 (2002). [15] A. W. Steiner, M. Prakash, J. M. Lattimer, and P. J. Ellis, Phys. Rep. 411, 325 (2005). [16] B. G. Todd-Rutel and J. Piekarewicz, Phys. Rev. Lett. 95, (2005). [17] M. Centelles, X. Roca-Maza, X. Vin as, and M. Warda, Phys. Rev. Lett. 102, (2009); M. Warda, X. Vin as, X. Roca-Maza, and M. Centelles, Phys. Rev. C 80, (2009). [18] A. Carbone et al., Phys. Rev. C 81, (R) (2010). [19] L. W. Chen et al., Phys. Rev. C 82, (2010). [20] B. A. Li, L. W. Chen, and C. M. Ko, Phys. Rep. 464, 113 (2008). [21] M. B. Tsang et al., Phys. Rev. Lett. 102, (2009). [22] C. J. Horowitz and J. Piekarewicz, Phys. Rev. Lett. 86, 5647 (2001). [23] J. Xu et al., Astrophys. J. 697, 1549 (2009). [24] A. W. Steiner, J. M. Lattimer, and E. F. Brown, Astrophys. J. 722, 33 (2010). [25] O. Moreno, E. Moya de Guerra, P. Sarriguren, and J. M. Udı as, J. Phys. G 37, (2010). [26] S. Ban, C. J. Horowitz, and R. Michaels, arxiv: [27] N. R. Draper and H. Smith, Applied Regression Analysis (Wiley, New York, 1998), 3rd ed. [28] K. Hebeler, J. M. Lattimer, C. J. Pethick, and A. Schwenk, Phys. Rev. Lett. 105, (2010). [29] A. W. Steiner and A. L. Watts, Phys. Rev. Lett. 103, (2009). [30] D. H. Wen, B. A. Li, and P. G. Krastev, Phys. Rev. C 80, (2009). [31] I. Vidan a, C. Provide ncia, A. Polls, and A. Rios, Phys. Rev. C 80, (2009). [32] T. Sil et al., Phys. Rev. C 71, (2005) symmetry energy 3/12

32 Pb Radius Neutron Radius From outer vs space to deepstar inside: exploring neutron skins of nuclei The 208Pb radius constrains the PHYSICAL REVIEW LETTERS 6, (2011) of neutron pressure matter at Equation Of State 1 NL subnuclear densities. Typel + Brown between P at I5 2 NL 1 G1 -RA NL -F1 3* NL 3 PCL-SH 1 N -PK NLK1 PC P V2 1 -S KA I2 NL TM1 F-P RH SV s G2 G 3 -T4 KO F-P 25 RH 3.s -Rs NL 24 1.s MP a M* PK 1 S -PC DD SIVSL0 A M M P old UG BC FS E1 -M y5 SL y4 DD -ME2 SL DD M* Linear Fit, r = find sharp correlation Nonrelativistic models Relativistic models 2/3 ρ0 and Rn. P 7 B-1 HFX 6 -T The NS radius depends on the pressure at nuclear density and above. Central density of NS few to 10 x nuclear density. Pb radius probes low density, NS radius medium density, and maximum NS mass probes high density equation of state. An observed softening of EOS with L (MeV)increase in pressure) density (smaller could Neutron stronglyskin suggest a transition (color online). of 208 Pb against slopeto exotic high density phase as ¼such 0:101 þ symmetryanenergy. The linear fit is!r np slope parameter quark or ain L. A sample testmatter, constraintstrange from a matter, 3% accuracy rawn. color superconductor II SG N D1 D1 B-8 HF k7 MS 0 9 v0 S J. Piekarewicz, CJH t. Then, we have to conclude that a 3% accuracy in s modest constraints on L, implying that some of ectations that this measurement will constrain L y may have to be revised to some extent. To narrow L, though demanding more experimental effort, a measurement of APV should be sought ultimately in Our approach can support it to yield a new accuracy!rnp! 0:02 fm and!l! 10 MeV, well below any s constraint. Moreover, PREX is unique in that the from a probe largely value of!rnp and LCAUfollows TION NEUTRO strong force uncertainties. mmary, PREX ought to be instrumental to pave the r electroweak studies of neutron densities in heavy [9,10,26]. To accurately extract the neutron radius n of 208 Pb from the experiment requires a precise ion between the parity-violating asymmetry APV se properties. We investigated parity-violating elecattering in nuclear models constrained by available ory data to support this extraction without specific tions on the shape of the nucleon densities. We trated a linear correlation, universal in the mean mework, between APV and!rnp that has very small Because of its high quality, it will not spoil the mental accuracy even in improved measurements of ith a 1% measurement of APV it can allow one to in the slope L of the symmetry energy to near a 0 MeV level. A mostly model-independent detern of!rnp of 208 Pb and L should have enduring on a variety of fields, including atomic parity servation and low-energy tests of the standard [8,9,32]. hank G. Colo, A. Polls, P. Schuck, and E. Vives uable discussions, H. Liang for the densities of F-PK and PC-PK models, and K. Kumar for inforon PREX kinematics. Work supported by the der Ingenio Programme CPAN CSD curvature parameter week ending 24 JUNE 2011 and Grants No. FIS from MEC and FEDER, No. 2009SGR-1289 from Generalitat de Catalunya, and No. N N from Polish MNiSW. The Good [1] Special issue on The Fifth International Conference on Exotic Nuclei and Atomic Masses ENAM 08, edited by M. Pfu tzner [Eur. Phys. J. A 42, 299 (2009)]. [2] G. W. Hoffmann et al., Phys. Rev. C 21, 1488 (1980). [3] J. Zenihiro et al., Phys. Rev. C 82, (2010). [4] A. Krasznahorkay et al., Nucl. Phys. A731, 224 (2004). [5] B. Kłos et al., Phys. Rev. C 76, (2007). [6] E. Friedman, Hyperfine Interact. 193, 33 (2009). [7] T. W. Donnelly, J. Dubach, and Ingo Sick, Nucl. Phys. Chiral EFT calc. of pressure P of neutron A503, 589 (1989). matter by et Hebeler al.cincluding [8] D. Vretenar al., Phys.et Rev. 61, three (2000). [9] neutron C. J. Horowitz, J. Pollock, P. A. Souder, forces S. (blue band) agree with and R. Michaels, Phys. Rev. 63, (2001). PREX results but Ctwo nucleon only [10] K. Kumar, P. A. Souder, R. Michaels, and G. M. Urciuoli, calculations yield smaller P. (see section Status and Plans for latest updates). [11] M. Centelles, X. Roca-Maza, X. Vin as, and M. Warda, Phys. Rev. C 82, (2010). [12] I. Angeli, At. Data Nucl. Data Tables 87, 185 (2004). [13] B. A. Brown, Phys. Rev. Lett. 85, 5296 (2000); S. Typel and B. A. Brown, Phys. Rev. C 64, (2001). [14] R. J. Furnstahl, Nucl. Phys. A706, 85 (2002). [15] A. W. Steiner, M. Prakash, J. M. Lattimer, and P. J. Ellis, Phys. Rep. 411, 325 (2005). [16] B. G. Todd-Rutel and J. Piekarewicz, Phys. Rev. Lett. 95, (2005). [17] M. Centelles, X. Roca-Maza, X. Vin as, and M. Warda, Phys. Rev. Lett. 102, (2009); M. Warda, X. Vin as, X. Roca-Maza, and M. Centelles, Phys. Rev. C 80, (2009). [18] A. Carbone et al., Phys. Rev. C 81, (R) (2010). [19] L. W. Chen et al., Phys. Rev. C 82, (2010). [20] B. A. Li, L. W. Chen, and C. M. Ko, Phys. Rep. 464, 113 (2008). [21] M. B. Tsang et al., Phys. Rev. Lett. 102, (2009). [22] C. J. Horowitz and J. Piekarewicz, Phys. Rev. Lett. 86, 5647 (2001). [23] J. Xu et al., Astrophys. J. 697, 1549 (2009). [24] A. W. Steiner, J. M. Lattimer, and E. F. Brown, Astrophys. J. 722, 33 (2010). [25] O. Moreno, E. Moya de Guerra, P. Sarriguren, and J. M. Udı as, J. Phys. G 37, (2010). [26] S. Ban, C. J. Horowitz, and R. Michaels, arxiv: [27] N. R. Draper and H. Smith, Applied Regression Analysis (Wiley, New York, 1998), 3rd ed. [28] K. Hebeler, J. M. Lattimer, C. J. Pethick, and A. Schwenk, Phys. Rev. Lett. 105, (2010). [29] A. W. Steiner and A. L. Watts, Phys. Rev. Lett. 103, (2009). [30] D. H. Wen, B. A. Li, and P. G. Krastev, Phys. Rev. C 80, (2009). [31] I. Vidan a, C. Provide ncia, A. Polls, and A. Rios, Phys. Rev. C 80, (2009). [32] T. Sil et al., Phys. Rev. C 71, (2005) symmetry energy The Bad 3/12

33 Pb Radius Neutron Radius From outer vs space to deepstar inside: exploring neutron skins of nuclei The 208Pb radius constrains the PHYSICAL REVIEW LETTERS 6, (2011) of neutron pressure matter at Equation Of State 1 NL subnuclear densities. Typel + Brown between P at I5 2 NL 1 G1 -RA NL -F1 3* NL 3 PCL-SH 1 N -PK NLK1 PC P V2 1 -S KA I2 NL TM1 F-P RH SV s G2 G 3 -T4 KO F-P 25 RH 3.s -Rs NL 24 1.s MP a M* PK 1 S -PC DD SIVSL0 A M M P old UG BC FS E1 -M y5 SL y4 DD -ME2 SL DD M* Linear Fit, r = find sharp correlation Nonrelativistic models Relativistic models 2/3 ρ0 and Rn. P 7 B-1 HFX 6 -T The NS radius depends on the pressure at nuclear density and above. Central density of NS few to 10 x nuclear density. Pb radius probes low density, NS radius medium density, and maximum NS mass probes high density equation of state. An observed softening of EOS with L (MeV)increase in pressure) density (smaller could Neutron stronglyskin suggest a transition (color online). of 208 Pb against slopeto exotic high density phase as ¼such 0:101 þ symmetryanenergy. The linear fit is!r np slope parameter quark or ain L. A sample testmatter, constraintstrange from a matter, 3% accuracy rawn. color superconductor II SG N D1 D1 B-8 HF k7 MS 0 9 v0 S J. Piekarewicz, CJH t. Then, we have to conclude that a 3% accuracy in s modest constraints on L, implying that some of ectations that this measurement will constrain L y may have to be revised to some extent. To narrow L, though demanding more experimental effort, a measurement of APV should be sought ultimately in Our approach can support it to yield a new accuracy!rnp! 0:02 fm and!l! 10 MeV, well below any s constraint. Moreover, PREX is unique in that the from a probe largely value of!rnp and LCAUfollows TION NEUTRO strong force uncertainties. mmary, PREX ought to be instrumental to pave the r electroweak studies of neutron densities in heavy [9,10,26]. To accurately extract the neutron radius n of 208 Pb from the experiment requires a precise ion between the parity-violating asymmetry APV se properties. We investigated parity-violating elecattering in nuclear models constrained by available ory data to support this extraction without specific tions on the shape of the nucleon densities. We trated a linear correlation, universal in the mean mework, between APV and!rnp that has very small Because of its high quality, it will not spoil the mental accuracy even in improved measurements of ith a 1% measurement of APV it can allow one to in the slope L of the symmetry energy to near a 0 MeV level. A mostly model-independent detern of!rnp of 208 Pb and L should have enduring on a variety of fields, including atomic parity servation and low-energy tests of the standard [8,9,32]. hank G. Colo, A. Polls, P. Schuck, and E. Vives uable discussions, H. Liang for the densities of F-PK and PC-PK models, and K. Kumar for inforon PREX kinematics. Work supported by the der Ingenio Programme CPAN CSD curvature parameter week ending 24 JUNE 2011 and Grants No. FIS from MEC and FEDER, No. 2009SGR-1289 from Generalitat de Catalunya, and No. N N from Polish MNiSW. The Good [1] Special issue on The Fifth International Conference on Exotic Nuclei and Atomic Masses ENAM 08, edited by M. Pfu tzner [Eur. Phys. J. A 42, 299 (2009)]. [2] G. W. Hoffmann et al., Phys. Rev. C 21, 1488 (1980). [3] J. Zenihiro et al., Phys. Rev. C 82, (2010). [4] A. Krasznahorkay et al., Nucl. Phys. A731, 224 (2004). [5] B. Kłos et al., Phys. Rev. C 76, (2007). [6] E. Friedman, Hyperfine Interact. 193, 33 (2009). [7] T. W. Donnelly, J. Dubach, and Ingo Sick, Nucl. Phys. Chiral EFT calc. of pressure P of neutron A503, 589 (1989). matter by et Hebeler al.cincluding [8] D. Vretenar al., Phys.et Rev. 61, three (2000). [9] neutron C. J. Horowitz, J. Pollock, P. A. Souder, forces S. (blue band) agree with and R. Michaels, Phys. Rev. 63, (2001). PREX results but Ctwo nucleon only [10] K. Kumar, P. A. Souder, R. Michaels, and G. M. Urciuoli, calculations yield smaller P. (see section Status and Plans for latest updates). [11] M. Centelles, X. Roca-Maza, X. Vin as, and M. Warda, Phys. Rev. C 82, (2010). [12] I. Angeli, At. Data Nucl. Data Tables 87, 185 (2004). [13] B. A. Brown, Phys. Rev. Lett. 85, 5296 (2000); S. Typel and B. A. Brown, Phys. Rev. C 64, (2001). [14] R. J. Furnstahl, Nucl. Phys. A706, 85 (2002). [15] A. W. Steiner, M. Prakash, J. M. Lattimer, and P. J. Ellis, Phys. Rep. 411, 325 (2005). [16] B. G. Todd-Rutel and J. Piekarewicz, Phys. Rev. Lett. 95, (2005). [17] M. Centelles, X. Roca-Maza, X. Vin as, and M. Warda, Phys. Rev. Lett. 102, (2009); M. Warda, X. Vin as, X. Roca-Maza, and M. Centelles, Phys. Rev. C 80, (2009). [18] A. Carbone et al., Phys. Rev. C 81, (R) (2010). [19] L. W. Chen et al., Phys. Rev. C 82, (2010). [20] B. A. Li, L. W. Chen, and C. M. Ko, Phys. Rep. 464, 113 (2008). [21] M. B. Tsang et al., Phys. Rev. Lett. 102, (2009). [22] C. J. Horowitz and J. Piekarewicz, Phys. Rev. Lett. 86, 5647 (2001). [23] J. Xu et al., Astrophys. J. 697, 1549 (2009). [24] A. W. Steiner, J. M. Lattimer, and E. F. Brown, Astrophys. J. 722, 33 (2010). [25] O. Moreno, E. Moya de Guerra, P. Sarriguren, and J. M. Udı as, J. Phys. G 37, (2010). [26] S. Ban, C. J. Horowitz, and R. Michaels, arxiv: [27] N. R. Draper and H. Smith, Applied Regression Analysis (Wiley, New York, 1998), 3rd ed. [28] K. Hebeler, J. M. Lattimer, C. J. Pethick, and A. Schwenk, Phys. Rev. Lett. 105, (2010). [29] A. W. Steiner and A. L. Watts, Phys. Rev. Lett. 103, (2009). [30] D. H. Wen, B. A. Li, and P. G. Krastev, Phys. Rev. C 80, (2009). [31] I. Vidan a, C. Provide ncia, A. Polls, and A. Rios, Phys. Rev. C 80, (2009). [32] T. Sil et al., Phys. Rev. C 71, (2005) symmetry energy The Bad 3/12