Measurement of the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mmultiscripts><mml:mi mathvariant="normal">H</mml:mi><mml:mprescripts /><mml:none /><mml:mn>2</mml:mn></mml:mmultiscripts><mml:mo>(</mml:mo><mml:mi>p</mml:mi><mml:mo>,</mml:mo><mml:mi>γ</mml:mi><mml:mo>)</mml:mo><mml:mmultiscripts><mml:mi>He</mml:mi><mml:mprescripts /><mml:none /><mml:mn>3</mml:mn></mml:mmultiscripts></mml:mrow></mml:math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>S…

Recent astronomical data have provided the primordial deuterium abundance with percent precision. As a result, big bang nucleosynthesis may provide constraint on universal baryon to photon ratio that is as precise as, but independent from, analyses of cosmic microwave background. However, such requires nuclear reaction rates governing production and destruction are sufficiently well known. Here, new measurement $^{2}\mathrm{H}{(p,\ensuremath{\gamma})}^{3}\mathrm{He}$ cross-section reported. This dominates error predicted abundance. A proton beam 400--1650 keV energy was incident solid titanium deuteride targets, emitted $\ensuremath{\gamma}$ rays were detected in two high-purity germanium detectors at angles ${55}^{\ensuremath{\circ}}$ ${90}^{\ensuremath{\circ}}$, respectively. The content targets has been obtained situ by $^{2}\mathrm{H}(^{3}\mathrm{He},p)^{4}\mathrm{He}$ offline using elastic recoil detection method. astrophysical $S$ factor determined center mass energies between 265 1094 keV, addressing uppermost part relevant range for complementary ongoing work lower energies. support higher temperatures than previously assumed, reducing