Ms = 6567.18; (* mass 7H *) 
Mb = 7482.538; (* mass 8He *) 
Mp = 938.272; (* mass proton *) 
Mt = 1875.612; (* mass 2H *) 
Mr = 2808.391; (* mass 3He *)

Kin = 1785.15; (* 8He lab momentum *)
K = (Mt/(Mb+Mt))Kin; (* 8He CM momentum *)
Kspf = (Ms/(Mt+Mb))Kin; 
Q = Mt+Mb - Ms - Mr;

(* Experimental data *)
ListPlot[{{1389.02,39.3154},{1387.88,107.979},{1457.79,116.475},{1368.38,63.0682},{1372.84,80.5056},{1357.17,127.918},{1394.55,43.3858},{1439.58,95.4774},{1434.13,80.2884},{1484.94,27.2899},{1422.21,42.4629},{1412.12,75.0641},{1425.49,46.9736},{1419.84,100.039},{1398.65,113.137},{1392.85,99.3859},{1468.78,95.4683},{1459.39,117.007},{1500.05,54.9053},{1384.36,66.8803},{1429.51,79.5188},{1463.08,75.1013},{1450.68,30.8627},{1456.02,62.5492},{1353.61,62.767},{1406.12,77.5984},{1433.17,108.769},{1491.08,107.173},{1354.55,59.2477},{1464.88,53.0533},{1486.89,103.347},{1415.14,31.5582},{1511.79,89.2272},{1473.36,94.964},{1389.65,97.6104},{1410.72,75.268},{1449.66,131.662},{1478.81,36.4432},{1501.63,70.209},{1427.5,71.6989},{1485.32,87.6881},{1394.9,104.39},{1418.37,53.7348},{1395.48,118.088},{1351.94,75.5284},{1435.29,73.9802},{1452.08,93.275},{1392.9,110.494},{1381.12,140.717},{1422.56,96.6324},{1477.89,45.0601},{1393.96,57.3387},{1499.1,119.505},{1412.7,101.04},{1395.25,65.5039},{1472.73,40.9895},{1474.64,105.297},{1537.18,75.9439},{1373.41,86.9221},{1445.61,59.8406},{1412.69,71.3945},{1397.05,116.721},{1445.75,111.077},{1398.9,112.506},{1422.59,69.3053},{1422.43,87.8568},{1511.31,90.2965},{1474.05,88.7992},{1419.26,47.9684},{1513.06,44.6139},{1409.45,79.1694},{1482.25,28.2982},{1448.13,83.532},{1567.94,50.0085},{1440.74,99.2754},{1350.27,83.4153},{1455.11,77.9635},{1575.43,82.3294},{1401.7,93.1979},{1459.86,106.666},{1341.55,56.818},{1400.06,84.6447},{1464.98,86.4061},{1502.51,80.6741},{1440.62,134.025},{1514.56,40.7018},{1400.28,100.476},{1432.5,80.1087},{1415.27,93.7499},{1439.72,101.148},{1463.96,57.1649},{1555.95,49.5586},{1387.94,84.5761},{1460.98,47.3052},{1390.31,83.5459},{1402.53,60.981},{1492.91,37.4615},{1513.74,35.9712},{1342.77,50.531},{1388.23,106.636},{1421.95,46.8927},{1445.92,67.734},{1413.96,103.136},{1397.9,57.1633},{1464.23,73.9079},{1424.35,115.425},{1357.17,49.6173},{1408.33,97.7933},{1421.46,126.275},{1391.35,57.225},{1414.18,35.7038},{1378.35,118.488},{1372.63,90.486},{1436.99,63.6512},{1434.92,101.299},{1443.73,112.714},{1469.12,99.3655},{1359.66,91.8886},{1462.98,51.56},{1461.06,60.0851},{1432.46,55.0352},{1427.69,29.1239},{1440.7,80.9748},{1396.96,78.1579},{1428.34,74.2909},{1402.55,59.6958},{1405.62,53.2945},{1387.32,76.8704},{1416.18,73.2998},{1516.39,82.0145},{1449.9,86.8282},{1424.7,79.8982},{1529.48,94.5894},{1356.08,67.2917},{1367.53,111.219},{1405.55,50.8611},{1413.35,123.263},{1466.34,47.5077},{1481.42,52.4973},{1507.32,62.754},{1434.46,79.9019},{1505.59,89.4594},{1477,66.8401},{1416.81,123.991},{1428.39,72.3758},{1421.94,58.8866},{1450.02,94.3017},{1442.69,80.9849},{1346.08,117.117},{1411.95,86.6569},{1433.83,106.405},{1436.52,90.7016},{1481.8,34.8477},{1411.26,116.767},{1420.15,94.8491},{1517.16,76.9966},{1508.79,50.191},{1410.47,84.889},{1422.28,128.904},{1463.81,64.4147},{1467.28,81.4779},{1412.11,104.963},{1486.24,103.275},{1507.34,43.4659},{1462.63,64.9401},{1384.27,56.5662},{1362.13,73.2949},{1440.04,54.9758},{1453.98,48.679},{1436.41,45.2403},{1414.07,45.2105},{1478.37,83.1502},{1525.06,75.9157},{1482.72,85.3788},{1398.7,98.5352},{1422.01,106.694},{1391.13,126.186},{1395.59,152.132},{1426.52,42.8167},{1437.8,44.7408},{1422.05,45.5207},{1404.49,92.7938},{1430.73,87.554},{1489.63,113.034},{1427.7,69.1493},{1403.08,66.1843},{1391.66,103.151},{1455.45,56.3519},{1418.7,74.1312},{1452.28,129.029},{1395.46,83.5876},{1452.46,121.378},{1493.66,62.8782},{1454.11,110.198},{1453,121.844},{1477.62,63.5259},{1468.95,52.8885},{1477.16,69.6552},{1494.88,65.5118},{1445.48,107.307},{1418.07,88.4897},{1361.88,61.8853},{1350.37,93.4765},{1350.17,62.5012},{1425.04,51.2142},{1453.48,81.2673},{1381.79,84.9552},{1408.87,86.4261},{1447.85,85.8618},{1482.51,46.3303},{1454.65,61.0901},{1435.65,81.6033},{1426.66,101.325},{1385.96,85.892},{1339.23,68.1402},{1401.95,63.8332},{1392.35,66.5745},{1560.17,53.0544},{1406.01,120.994},{1525.18,84.481},{1442.43,74.9458},{1399.25,76.3413},{1425.45,80.2992},{1468.28,60.1306},{1411.19,99.2105},{1452.47,74.9466},{1407.26,120.753},{1466.31,84.2442},{1398.43,83.1676},{1533.56,101.516},{1448.48,77.8566},{1441.42,37.5883},{1388.19,114.616},{1394.17,55.018},{1455.49,113.947},{1395.36,88.1556},{1392.55,59.5768},{1444.11,58.9804},{1466.56,87.9559},{1372.88,91.6193},{1387.2,91.2921},{1434.98,96.4451},{1382.18,97.896},{1459.02,85.6234},{1428.42,98.8822},{1405.12,124.009},{1489.48,101.851},{1459.34,114.651},{1408.67,82.8126},{1386.89,56.3118},{1533.06,71.8982},{1460.22,123.196},{1370.22,62.1697},{1548.81,81.9262},{1393.46,111.565},{1464.98,83.1582},{1419.41,93.1336},{1453.73,120.889},{1485.38,47.7615},{1426.92,105.4},{1434.94,80.5513},{1361.33,69.3275},{1457.21,74.9202},{1524.3,91.6699},{1425.77,81.4342},{1491.76,49.928},{1496.58,71.2074},{1473.32,41.3837},{1422.85,144.581},{1426.04,118.882},{1417.9,64.144},{1468.9,81.6244},{1472.8,87.5776},{1364.42,128.504},{1475.09,94.7571},{1485.33,123.54},{1425.54,77.7769},{1443.28,77.9664},{1430.94,111.944},{1503.6,27.062},{1440.02,8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Ebal[Kpar_,Kperp_]:= ((Kin^2)/(2 Mb))+ Q - (((Kpar^2)+(Kperp^2))/(2 Ms)) - (((((Kin-Kpar))^2)+(Kperp^2))/(2 Mr))

(*ContourPlot[Ebal[Kpar,Kperp],{Kpar,800,1785.15`},{Kperp,0,400},Contours->{0,2,6,8,19,12,16,20,24},ContourLabels->True,Epilog->{Line[{{1350,40},{1500,20}}],Line[{{1500,20},{1570,70}}],Line[{{1570,70},{1400,150}}],Line[{{1400,150},{1350,120}}],,Line[{{1350,120},{1350,40}}]}]*)
Show[ContourPlot[Ebal[Kpar,Kperp],{Kpar,800,1785.15`},{Kperp,0,400},Contours->{0,2,6,8,19,12,16,20,24},ContourLabels->True],ListPlot[{{1389.02,39.3154},{1387.88,107.979},{1457.79,116.475},{1368.38,63.0682},{1372.84,80.5056},{1357.17,127.918},{1394.55,43.3858},{1439.58,95.4774},{1434.13,80.2884},{1484.94,27.2899},{1422.21,42.4629},{1412.12,75.0641},{1425.49,46.9736},{1419.84,100.039},{1398.65,113.137},{1392.85,99.3859},{1468.78,95.4683},{1459.39,117.007},{1500.05,54.9053},{1384.36,66.8803},{1429.51,79.5188},{1463.08,75.1013},{1450.68,30.8627},{1456.02,62.5492},{1353.61,62.767},{1406.12,77.5984},{1433.17,108.769},{1491.08,107.173},{1354.55,59.2477},{1464.88,53.0533},{1486.89,103.347},{1415.14,31.5582},{1511.79,89.2272},{1473.36,94.964},{1389.65,97.6104},{1410.72,75.268},{1449.66,131.662},{1478.81,36.4432},{1501.63,70.209},{1427.5,71.6989},{1485.32,87.6881},{1394.9,104.39},{1418.37,53.7348},{1395.48,118.088},{1351.94,75.5284},{1435.29,73.9802},{1452.08,93.275},{1392.9,110.494},{1381.12,140.717},{1422.56,96.6324},{1477.89,45.0601},{1393.96,57.3387},{1499.1,119.505},{1412.7,101.04},{1395.25,65.5039},{1472.73,40.9895},{1474.64,105.297},{1537.18,75.9439},{1373.41,86.9221},{1445.61,59.8406},{1412.69,71.3945},{1397.05,116.721},{1445.75,111.077},{1398.9,112.506},{1422.59,69.3053},{1422.43,87.8568},{1511.31,90.2965},{1474.05,88.7992},{1419.26,47.9684},{1513.06,44.6139},{1409.45,79.1694},{1482.25,28.2982},{1448.13,83.532},{1567.94,50.0085},{1440.74,99.2754},{1350.27,83.4153},{1455.11,77.9635},{1575.43,82.3294},{1401.7,93.1979},{1459.86,106.666},{1341.55,56.818},{1400.06,84.6447},{1464.98,86.4061},{1502.51,80.6741},{1440.62,134.025},{1514.56,40.7018},{1400.28,100.476},{1432.5,80.1087},{1415.27,93.7499},{1439.72,101.148},{1463.96,57.1649},{1555.95,49.5586},{1387.94,84.5761},{1460.98,47.3052},{1390.31,83.5459},{1402.53,60.981},{1492.91,37.4615},{1513.74,35.9712},{1342.77,50.531},{1388.23,106.636},{1421.95,46.8927},{1445.92,67.734},{1413.96,103.136},{1397.9,57.1633},{1464.23,73.9079},{1424.35,115.425},{1357.17,49.6173},{1408.33,97.7933},{1421.46,126.275},{1391.35,57.225},{1414.18,35.7038},{1378.35,118.488},{1372.63,90.486},{1436.99,63.6512},{1434.92,101.299},{1443.73,112.714},{1469.12,99.3655},{1359.66,91.8886},{1462.98,51.56},{1461.06,60.0851},{1432.46,55.0352},{1427.69,29.1239},{1440.7,80.9748},{1396.96,78.1579},{1428.34,74.2909},{1402.55,59.6958},{1405.62,53.2945},{1387.32,76.8704},{1416.18,73.2998},{1516.39,82.0145},{1449.9,86.8282},{1424.7,79.8982},{1529.48,94.5894},{1356.08,67.2917},{1367.53,111.219},{1405.55,50.8611},{1413.35,123.263},{1466.34,47.5077},{1481.42,52.4973},{1507.32,62.754},{1434.46,79.9019},{1505.59,89.4594},{1477,66.8401},{1416.81,123.991},{1428.39,72.3758},{1421.94,58.8866},{1450.02,94.3017},{1442.69,80.9849},{1346.08,117.117},{1411.95,86.6569},{1433.83,106.405},{1436.52,90.7016},{1481.8,34.8477},{1411.26,116.767},{1420.15,94.8491},{1517.16,76.9966},{1508.79,50.191},{1410.47,84.889},{1422.28,128.904},{1463.81,64.4147},{1467.28,81.4779},{1412.11,104.963},{1486.24,103.275},{1507.34,43.4659},{1462.63,64.9401},{1384.27,56.5662},{1362.13,73.2949},{1440.04,54.9758},{1453.98,48.679},{1436.41,45.2403},{1414.07,45.2105},{1478.37,83.1502},{1525.06,75.9157},{1482.72,85.3788},{1398.7,98.5352},{1422.01,106.694},{1391.13,126.186},{1395.59,152.132},{1426.52,42.8167},{1437.8,44.7408},{1422.05,45.5207},{1404.49,92.7938},{1430.73,87.554},{1489.63,113.034},{1427.7,69.1493},{1403.08,66.1843},{1391.66,103.151},{1455.45,56.3519},{1418.7,74.1312},{1452.28,129.029},{1395.46,83.5876},{1452.46,121.378},{1493.66,62.8782},{1454.11,110.198},{1453,121.844},{1477.62,63.5259},{1468.95,52.8885},{1477.16,69.6552},{1494.88,65.5118},{1445.48,107.307},{1418.07,88.4897},{1361.88,61.8853},{1350.37,93.4765},{1350.17,62.5012},{1425.04,51.2142},{1453.48,81.2673},{1381.79,84.9552},{1408.87,86.4261},{1447.85,85.8618},{1482.51,46.3303},{1454.65,61.0901},{1435.65,81.6033},{1426.66,101.325},{1385.96,85.892},{1339.23,68.1402},{1401.95,63.8332},{1392.35,66.5745},{1560.17,53.0544},{1406.01,120.994},{1525.18,84.481},{1442.43,74.9458},{1399.25,76.3413},{1425.45,80.2992},{1468.28,60.1306},{1411.19,99.2105},{1452.47,74.9466},{1407.26,120.753},{1466.31,84.2442},{1398.43,83.1676},{1533.56,101.516},{1448.48,77.8566},{1441.42,37.5883},{1388.19,114.616},{1394.17,55.018},{1455.49,113.947},{1395.36,88.1556},{1392.55,59.5768},{1444.11,58.9804},{1466.56,87.9559},{1372.88,91.6193},{1387.2,91.2921},{1434.98,96.4451},{1382.18,97.896},{1459.02,85.6234},{1428.42,98.8822},{1405.12,124.009},{1489.48,101.851},{1459.34,114.651},{1408.67,82.8126},{1386.89,56.3118},{1533.06,71.8982},{1460.22,123.196},{1370.22,62.1697},{1548.81,81.9262},{1393.46,111.565},{1464.98,83.1582},{1419.41,93.1336},{1453.73,120.889},{1485.38,47.7615},{1426.92,105.4},{1434.94,80.5513},{1361.33,69.3275},{1457.21,74.9202},{1524.3,91.6699},{1425.77,81.4342},{1491.76,49.928},{1496.58,71.2074},{1473.32,41.3837},{1422.85,144.581},{1426.04,118.882},{1417.9,64.144},{1468.9,81.6244},{1472.8,87.5776},{1364.42,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]]

(* ListPlot + Show   ListPlot[testData,PlotMarkers->"*",PlotStyle->Red]*)