1. Plan 3He(4He, )7Be, Nuclear Astrophysics at Weizmann Institute.
S34 –factor
Experiment & Results
7Li and S34.
Future
Thank you very much for giving me the opportunity to speak about our work.
I would like to mention about the experiments that we are presently interested, and then come to the main topic of S34-factor or the cross section measurement on 3He + 4He producing 7Be. After giving the results I would like to briefly go through the relevance of the present measurement in connection with the 7li abundance and finally few words about our immediate plans.
B.S. Nara Singh HRI
11/19/2018

2. Nuclear Astrophysics around A ~ 7
7Be(p,g)8B ISOLDE + VDG
3He(4He,g)7Be VDG
7Li + 3He and 7Be + 3He VDG
4He(8Li,n)11B
RIB’S (ISOLDE, ..)
“Hot” p-p chain }
Solar Neutrinos
SBBN, 7Li }
Nucleo-Synthesis
On the nuclear astrophysics side our group concentrates on the cross section measurements of reactions involving nuclei around mass 7 listed here.
Most of these experiments, we carry out using VDG and ISOLDE facility. 7Be(p,g) and 3He(a,g) reactions are relevent to solar neutrinos. Others are to nucleo-synthesis. In particular 7li+3he etc. play important role in understanding 11C and 7Li abundances. For these experiments we have published or final results. We also have plans to study several other reactions. Such as 8Li(alpha,n) which plays an important role in IBBN models as most of the heavy nuclie must pass through 11B. It also plays an important role in understanding the Type 2 supernova. Using RIB facility in ISOLDE we plan to study Hot pp-chain.
“Heavy” Elements
Massive Stars }
B.S. Nara Singh HRI
11/19/2018

3. Nuclear Astrophysics with RIB’S
8B(p,)9C
8B(,p)11C
9C(,p)12N
11C(p,)12N
In particular the following reactions and these play signifacant role in deciding the fate of the low metallicity stars. The other reaction that we are interested in is 14(alpha,p) which occurs in x-ray bursters scenarios as a waiting point reaction and connects CNO to rp-processes resulting in medium mass nuclei.
Today I will be speaking about…
x-ray bursters
14O(a,p)17F
Fate of Low metallicity stars
B.S. Nara Singh HRI
11/19/2018

4. A New Precision Measurement of the 3He(4He, )7Be Cross Section
B.S. Nara Singh and M. Hass
Weizmann Institute of Science, ISRAEL
G. Haquin and Y. Nir-El
SOREQ, ISRAEL
Today, I will be speaking about our new precision measurements on cross seciton of 3HeCapture by 4He producing 7Be.
This reaction is important because right now it is the major source of uncertainty in the solar neutrino flux calculation.
These experiments We carried out using VDG accelerator at WIS and a gamma counting setup at SOREQ lab Israel.
B.S. Nara Singh HRI
11/19/2018

5. PP-Chain and Solar Neutrinos
The 4he producetion in the sun through proton fusion in the sun results in electron type neutrinos. And the whole of PP chain their energy range from 0 to 14 MeV.
The neutrinos that are produced in the this reaction we refer to as 7Be neutrinos and in this reaction 8B neutrinos. Some of solar neutrino experiments detected this electron type neutrino flux to be 1/3rd of what was predicted and this ofcourse is the solar neutrino puzzle.
Produces 7Be and 8B neutrinos
B.S. Nara Singh HRI
11/19/2018

6. Solar Neutrino Experiments
Some of solar neutrino experiments detected this electron type neutrino flux to be 1/3rd of what was predicted and this ofcourse is the solar neutrino puzzle.
~1/3rd of predicted neutrino flux detected
B.S. Nara Singh HRI
11/19/2018

7. The SNO (Sudbury Neutrino Observatory) Experiment
A D2O Detector
Elastic
Mostly ne
nx +e nx+e-
ne + d p + p + e-
charge current
Only ne
nx + d p + n + nx
neutral current
All flavors
Then came the D20 detector at Sudbery neutrino observatory and detects the solar neutrinos via elastic scattering mostly electron type neutinos, Charge current only electron type neutrinosand Neutral current and all flavours processes. Unlike the ealier cases where only electron type neutrino was detected. The results from these detection have been published in these papers.
YES!!
PRL 87, (2001)
PRL 89, (2002)
PRL 92, (2004)
B.S. Nara Singh HRI
11/19/2018

8. SNO and Standard Solar Model
No More a Puzzle!!
The red-green-blue bands corresponds to results from these detections. On the x-axis we have electron type neutrino flux and on y axis for other flavours. Widths represent 1 sigma errors. And this is from Standards model cross section.
The measured solar netutrino fluxes are understood using neutrino oscillations. In particular in this case the electron trype neutrino is transformed into the other two flavours and hence there was a deficiency in the electron type neutrinos. No more solar neutrino problem.
Oscillations
R. Gandhi et al.
hep-ph/
Errors to be reduced
B.S. Nara Singh HRI
11/19/2018

9. BOREXINO and Sharp 7Be electron capture line.
Here are several other experiments and their energy thresholds proceeding futher in this direction. Out of these the Borexino experiment of special interest because it is sensititive to the sharp neutrino line around 0.8 MeV coming from electron capture of 7Be. And this will have more precise results on the oscillation parameters. And the present measurement on S34 factor is also timely in this respect.
Precise Osc. Parameters.
Timely S34 measurement.
B.S. Nara Singh HRI
11/19/2018

10. Uncertainties to SSM Major part of Uncertainties
come from Nuclear reaction
Cross sections
So now the experimental and estimated solarneutrino fluxes basically agrees and now it is the question of reducing errors. For standard solar models, Major part of it comes from Nuclear reaction cross-sections.
B.S. Nara Singh HRI
11/19/2018

11. SSM Calculations Large Errors on 8B and 7Be neutrinos
Major contributions from Relevant Nuclear Reaction Cross sections.
This slide gives the Standard Solar Model Calculations of these neutrino fluxes. 7Be and 8B have large errors. The major contribution comes from the measured cross-sections of responsible Nuclear reactions. There has been lot of effort to reduce these errors.
B.S. Nara Singh HRI
11/19/2018

12. Two New Measurements on 7Be(p,)8B, S17 1999- M. Hass et al
Two New Measurements on 7Be(p,)8B, S M. Hass et al., (PLB 462, 237) L.T. Baby et al., (PRL 90, )
~ 10 new determinations
In the last 10 years only!
Only 4% error contribution
Recently the corss section for the proton capture by 7be has been measured by several groups including ours. And the result is now we know this cross-section precisely. And it contibuted only a 4% error to the calculations
7Be(p,g)8B “saga” is
(perhaps) not over
S17(E) = E  (E) exp(2)
B.S. Nara Singh HRI
11/19/2018

13. 3He(4He,)7Be, S34 7 ( 8 % ) S34(0)0.86 8 ( 8 %)  S34(0)0.81
Major Source of Uncertainty Bahcall et al., PRL (2004)
7 ( 8 % ) S34(0)0.86
8 ( 8 %)  S34(0)0.81
. On the other hand the cross section of 3he capture by 4he contributed to 8% error to both 7Be and 8B neutrinos and enters as S34 in SSM. Where S34 is related to the cross section through this relation.
This trongly recommends for new precision measurements. And it is surprising that there has been no measurement on this reaction for last 15 years.
The present measurement is also timely in the view of Borexino experiment and its sensititivity to the sharp neutrino line around 0.8 MeV coming from electron capture of 7Be. And also plays an important role in understanding the 7Li abundances.
S34(E) = E  (E) exp(2)
No measurement for last 15 years.
New precision measurements Highly Recommended.
B.S. Nara Singh HRI
11/19/2018

14. 3He(4He,)7Be, 7Li
Now, the importance of s34 regarding 7Li abundances is discussed in this paper by Cyburt et al. And this very reaction turns out to be the majore source due to the large discrepancies in the available data. And the measurement below 0.5 MeV are highly recommended.
One of the major uncertainties in the issue of 7Li abundances R. Cyburt PRD 70, (2004)
Measurements with E~0.5 MeV Highly Recommended.
B.S. Nara Singh HRI
11/19/2018

15. Gamow peak and S(0) Krawinkel et al Convincing Results!
100 keV
22(6) keV
Krawinkel et al
In the sun these reactions take place around 22keV –Gamow peak. Where as in the lab one tries to go as low in energy as possible., trying to reach the Gamow peak. For e.g. Krawinkel et al. has measured the cross-sections for 3He capture by 4He starting from 1.4MeV down to 100keV, going down by a factor of 1000 in cross section. As we can see these results are convincing and a 10 % accurate value for S(0) is obtained. Now why do we talk about more results.
Convincing Results!
Why more experiments ?
B.S. Nara Singh HRI
11/19/2018

16. Prior to the present work
Energy dependence Consistent, But Significant scatter
Adelberger etal., RMP 70, 1265 (1998) S34 = 0.53(5)
Angulo et al. NPA , 656 (1999) S34 = 0.53(9)
Large errors at Medium Ecm, Absolute scale to be fixed!!!
If we look at this compilation from the existing data of different experiments shown separately together with the theoretical fits. And all of them together. We can see two things. Energy dependence among different groups is consistent. But there is a large scatter. From this Adelberger et al recommends a 10% accurate value for S34(0) while Angulo et al recommends 16% accurate value. Definitely these errors can be reduced. And one possibility in this direction is to fix the absolute scale and reduce the errors at medium energies.
B.S. Nara Singh HRI
11/19/2018

17. Two methods Prompt vs Activity Discrepency?….
Prompt-: DC  429, 429  0
Complicated Setups
S34 = (16)
Activity- 478 keV : 7Be decays to 7Li
BR=10.45 (4) % T1/2=53.29 (7) days
Simple setups
S34 = 0.572(26)
Adelberger et al., RMP 70, 1265 (1998).
3He and 4He at certain c.m. energy poulate 7be at an excited level and the gamma-decay proceeds promptly. From these gamma intensities one can obtained the cross-sections. This involves complicated setups. One can also do the same by observing the 7Be 478 keV gamma decay to 7Li using the known BR and T1/2. These involve simple setups. Results from these two methods suggest an apparent discrepency. Now is this so. We will come to this point in the end.
Prompt vs Activity Discrepency?….
B.S. Nara Singh HRI
11/19/2018

18. Present Strategy
Simple setup with 3He beam, 4He gas traget and Ni foil.
Precision measurements at 950 keV under varying experimental conditions.
Measurements at few Ecm keV.
“Benchmark” to compare with previous data and the future data at lower energies.
S34(0) extrapolation using all of the data and theoretical fits.
Only Few Previous Activity Measurements. Best suitable for medium energies.
If we look at once again the existing data, but now distinguishing prompt and decay gamma measurement, we see that decay gamma measurements are low in number. However, from these high energy points we can see that the activity measurements are best suitable at these energies.
Hence our strategy is to carry out several accurate measurements at 950 keV and then proceed down to 400 keV. Since for low energies the method is suitable . We check our data against the existing data from prompt gamma measurements. Finally we use all the data to extract S(0) using the theoretical extracpolations.
B.S. Nara Singh HRI
11/19/2018

19. Experimental Setup 27Al(p,g)28Si 10B(,p)13C Cross-check CI on Chamber
Resonances
27Al(p,g)28Si
10B(,p)13C
Cross-check
-400 V
CI on Chamber
This is the schematic diagram of our experimental setup. Inside the Chamber 4He gas typically of … thickness is filled. Pressure is monitored. And the Ni foil of .. Thickness takes the pressure difference of the beam line. Beam is scanned to avoid the damage due to localized heating. The current is measured on the Chamber+catcher. The suppressor operated at –400V allowed a true CI Measurement. Scattered beam is detected for cross-check. The beam energies are calibrated using H2 and H3 beam and 27Al(p,g) resonances. Eloss and Straggling are checked with 10B(a.p)13C resonances. Also for the cross check on the estimation of beam heating.
50 – 120 g/cm2
1.0 m, Raster scan
B.S. Nara Singh HRI
11/19/2018

20. Setup and Simplicity
7Be implanted into a Cu catcher few m depth and within a circle of 20 mm dia
In this photo we can see the light produced as the beam passes through the target gas. And the Ni foil. The 7 Be produced inside the chamber are implanted into a Cu catcher at few um depth and within a cicle of 20 mm dia.
B.S. Nara Singh HRI
11/19/2018

21. 1000 counts in 478 peak. Y =  Np Nt
Activity Measured At SOREQ Lab; 3-6 days , low background.
Efficiency correction for Extended Target  1.3%
Y =  Np Nt
Gamma activity measurements were done at SOREQ lab using a HPGe setup. Where we have low background. The detectors are efficiency calibrated at 478 keV using well calibrated reference point 2mm source. The number of 7Be in the reference source were know to 0.7% from our earlier measurements and this allowed a very accurate extraction of 7Be implanted in to the catchers.
This is the typical background spectra and as we can see there is no interfering peak around 478 keV. This is the low statistics spectrum from the catcher prepared at 425keV. Typically the gamma counting is done till we acquire 1000 counts in 478 keV line. From this gamma yield the sigma are obtained.
N(7Be, t=t0) = 2.667(18) • A 0.7% determination at two separate laboratories, SOREQ (IL) and TA&M, Baby et al. PRL 90, (2003)
B.S. Nara Singh HRI
11/19/2018

22. Errors: Statistics, 3 – 5 % Ec.m., 2 – 7 % Np, 1- 2 % P < 1 %
B.S. Nara Singh1, M. Hass1, Y. Nir-El2 and G. Haquin2
1. Dept. of Particle Physics, The Weizmann Institute, Rehovot ISRAEL
2. Soreq Research Center, Yavne ISRAEL
Accepted for the publication in Phys. Rev. Lett.
Errors:
Statistics, 3 – 5 %
Ec.m., 2 – 7 %
Np, 1- 2 %
P < 1 %
Tc<0.5 %
Ni foil, < 2 %
Here we summarize the results. We have 6 measurements around 950keV under different experimental conditions. Resulting in a precise cross section. We have two measurments around 600 keV resulting in accurate measurments. And somewhat less accurate measurements at lower energies.
Main contributions to the errors came from the statistics and the Ec.m.
B.S. Nara Singh HRI
11/19/2018

23. Compatibility check Hilgemeier et al. fully consistent with
Normalized with
a factor of 1.4
[15] Krawinkel ’82
[10] Hilgemeier ’88
[11] Osborne ’84
[13] Parker ’63
[14] Nagatani ‘69
In this table we check the compatibility of our data with the data from Krawinkel etal., Hilgemier et al and others. Krawinkel etal data is taken after normalizing with 1.4 factors as suggested by Hilgemeir et al. As we can see Hilg et al. data is in full consistency with our data at an Absolute scale.
Hilgemeier et al. fully consistent with
the present work In Absolute Scale.
B.S. Nara Singh HRI
11/19/2018

24. Final Result S34(0) Data NO need for assumed distinction between
prompt-decay g results
S34(0)
Data
0.53(2)(1)
Present
0.53(3)(1)
+Hilgemeier
+Krawinkel
Final
Renormalized
Here are the present data with some of the representative theoretical fits. For comparison we also give the data from Hilgemeir et al. Inset presents this data together with renormalized Krawinkel et al s data. And the fits to the entire data. This table summarizes the results. Fits to the present and +Hilgemeir and+Renormalized Krawinkel. And Finally the recommended value.
All these results as we can see are essensially the same and at this points it should be pointed out that there is no need for assumed distinctions between prompt-decay gamma measurements.
Experimental Model
B.S. Nara Singh HRI
11/19/2018

25. Neutrino Fluxes Uncertainty in 7 and 8 from 8 % to 5 %
Adelberger et al., RMP 70, 1265 (1998) to the present.
S34 = 0.53(5) to 0.53(3) keV-barn
Uncertainty in 7 and 8 from 8 % to 5 %
The present result takes the uncertainties in 7be and 8B neutrino fluxes from 8% to a level of 5%
B.S. Nara Singh HRI
11/19/2018

26. Neutrino Fluxes 3He(4He,g)7Be “saga” Is continuing?...
The 8 to 5 % reduction takes away s34 from being a major source of uncertainty. But more experiments towards better accuracies are welcome.
B.S. Nara Singh HRI
11/19/2018

27. Nucleo-synthesis in SBBN
A. Coc Trento’04
The twelve main reactions used in the Standard Big bang Nucleo systhesis Calculations. As we can see 3he(4he, g) reaction plays a role. And the measured cross sections for these reactions enter into the calculations.
B.S. Nara Singh HRI
11/19/2018

28. Abundances, Sensitivity to 
The calculated abundances using NACRE compilation, showing the sensitivity to baryon-to-photon ratio.
As we can see a pronounced sensitivity is exhibited by 7Li, 7Be abundances.
And for other lighter nuclei the sensitivity is lesser. Eta to be fixed from Observations.
B.S. Nara Singh HRI
11/19/2018

29. Here the abundances form the observations
Here the abundances form the observations. Eta has to be fixed in order to understand these abundances.
B.S. Nara Singh HRI
11/19/2018

30. WMAP B.S. Nara Singh HRI 11/19/2018
Wilkinson Microwave Anisotropy Probe mission. This is the temperature map of the sky. Obtained from the observation of Anisotropies of Cosmic Microwave background. Here I also list some of the other observations.
B.S. Nara Singh HRI
11/19/2018

31. From the fourier transform of this map the parameter eta is obtained.
B.S. Nara Singh HRI
11/19/2018

32. S34 = 0.54(9)/0.53(5) keV-b B.S. Nara Singh HRI 11/19/2018
7Li abundances with 1 sigma width, against the baryon to photon ratio.
The blue curve is from the calculations.
Hatched region, Obtained from different primitive astrophysical sites.
Vertical stripe (1sigma) limits on eta obtained from WMAP.
B.S. Nara Singh HRI
11/19/2018

33. What is the source for this discrepency?
Here we can see a clear agreement between the observed and the calculated D abundances using eta value obtained from WMAP. Where as a clear discrepency in 7Li abundances. Where is the problem.
What is the source for this discrepency?
B.S. Nara Singh HRI
11/19/2018

34. 7Li Abundances in SBBN and S34
Here are the 10 main reactions and its sensitivities to the abundances. Roughly representing the relative uncertainty contributions. As we can see S34 for exaple has major contributions. S34 value used for Stardard BBN is of 16 %. The present result of 5% accuracy will reduce the error. However this will not take away the discrepency between the observations and calculations. And solution may lie some where else.
Coc et al. ApJ 600 (2004) 544
B.S. Nara Singh HRI
11/19/2018

35. Look for other solutions
7Li and S34
Look for other solutions
Angulo et al. NPA , 656 (1999) S34 = 0.53(9)
Uncertainty Reduced from arb fact to 0.18.
But S34 is not the limiting factor.
Now, the present result reduce this uncertainty. But does’t solve the problem. So one has to look for other solution.
B.S. Nara Singh HRI
11/19/2018

36. 7Be(p,)8B, S17
Aim to reduce the error further and go below 4% error contribution.
Improved theoretical calculations
P. Descouvemont et al, to be published in Phys. Rev. C.
A. Csoto et al. Private communication.
Recently the corss section for the proton capture by 7be has been measured by several groups including ours. And the result is now we know this cross-section precisely. And it contibuted only a 4% error to the calculations
B.S. Nara Singh HRI
11/19/2018

37. Method
Implanted 7Be target Laser Ion Source, ISOLDE, CERN, Nov 04
precise number of target atoms and known profile.
Proton beam from VDG Dec04-Jan05, Well calibrated for energies and high A currents. Scanned for uniformity..
Delayed  particle detection following the - decay (770 ms).
8B8Be  2
Now, the present result reduce this uncertainty. But does’t solve the problem. So one has to look for other solution.
B.S. Nara Singh HRI
11/19/2018

38. Low energy Cross sections of 7Be(p,)8B, S17; Setup
New chamber specially made to
handle highly active target.
Larger number of target atoms.
Larger Beam currents, with the
Target and Stepper motor cooling
Collimator, Aligned Within 0.1 mm
Stepper motor, 1.5 s for beam on and counting,
Rotation: 100 ms +100 ms
Now, the present result reduce this uncertainty. But does’t solve the problem. So one has to look for other solution.
With ~ Be target atoms and few A currents and longer beam
times we aim to increase the experimental accuracies by a factor of 2.
B.S. Nara Singh HRI
11/19/2018

39. 7Be decay rate Applicable to Nuclear waste disposal.
~1% medium effect, on EC decay due to change in 7Be valence electrons. C60w.r.t. 7Be medium, 0.8%. T. Ohtsuki et al.., PRL 93, (2004)
Initiation of systematic studies in, metals, C60, inorganic fullerines, semi-conductors etc.
Implanted targets were prepared, Nov04;these would result in more precise measurements in comparison with the available data.
SNP: Only 0.5% effects on SSM calculations. Eventually will become important.
Applicable to Nuclear waste disposal.
Now, the present result reduce this uncertainty. But does’t solve the problem. So one has to look for other solution.
B.S. Nara Singh HRI
11/19/2018

40. Thanks B.S. Nara Singh HRI 11/19/2018
Now, the present result reduce this uncertainty. But does’t solve the problem. So one has to look for other solution.
B.S. Nara Singh HRI
11/19/2018