Hagedorn Model Research Articles

The cosmic microwave background and the hadron era of the early universe: A possible connection

A cosmological model is constructed which is a Friedman model, but with a finite ultimate temperature ( T F ). A plausible argument is presented which suggests that the existence of T F and the cosmic microwave background restricts the form of the hadronic level density: ▪, where A, B = constants. In our model, B = 7 2 − 3 s , where s = positive integer. The case s = 3 (B = 5 2 ) is the well-known Hagedorn model; the Frautschi model corresponds to s = 6 ( B = 3); the cases s = 1 (B = 1 2 ) and s = 2 ( B = 2) have not been considered before now. For each value of B < 7 2 , the model gives the temperature ( T γ0 ) of the microwave background as a function of A, T F and ϱ 0 (the present energy density of the universe). Two fascinating results then emerge: first, all estimates of T γ0 favor a low density Friedman universe ( ϱ0 = 10 −31 g/ cm 3), which rules out a universe with positive curvature; second, for ϱ 0 = 10 −31 gr/ cm 3 the best estimate of T γ0 (⊃3K) occurs for the Hagedorn model.

Quarks as a Thermometer for Cosmologies

view Abstract Citations (16) References (24) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Quarks as a Thermometer for Cosmologies Frautschi, Steven ; Steigman, Gary ; Bahcall, John Abstract If physical quarks exist, their density relative to ordinary baryons (nq/flB) depends sensitively on the highest temperatures reached during cosmological evolution. Zel'dovich has pointed out that in the conventional hot big bang with a limited spectrum of elementary particles the quark density flq/flB predicted for the present time is much larger than the experimental upper bound. In the present paper we derive the consequences for conventional cosmologies of the Hagedorn type of hadron spectrum which implies a "warm" limiting temperature of order kT 160 MeV. With initial temperatures of this order, the predicted flq/flB is consistent with present experimental limits if the quark mass exceeds 9 GeV. In the Hagedorn model, quarks with rn, > 9 GeV would be very difficult to produce in accelerator experiments because of statistical competition; searches for fossil quarks in bulk matter seem to offer the only hope of detection. We also discuss predictions for the quark density in several less conventional cosmologies (mix master, Brans-Dicke, Lemaitre, steady state, and Klein-Alfven) and with forms of the hadron density of states that differ from Hagedorn's proposed form Publication: The Astrophysical Journal Pub Date: July 1972 DOI: 10.1086/151558 Bibcode: 1972ApJ...175..307F full text sources ADS |

Distribution of transverse and longitudinal momentum in π−p interactions at 7.0 GeV/c

We have measuredpt andpi spectra of the pions and protons produced in six- and two-prong interactions in a bubble-chamber experiment. The BNL 80 in, liquid-hydrogen bubble chamber was exposed to a 7.0 GeV/c negative-pion beam. The data are analysed in terms of the Hagedorn model and the two-temperature model of Wayland and Bowen. The temperature of the interaction volume obtained from fitting thept spectra of the pions is below 140 MeV, and for the protons it is close to 180 MeV. Thept spectra of the pions yields a good fit to an expression given in the two-temperature model. We have divided our six-prong data into peripheral and nonperipheral events and the temperature values of the two samples show considerable difference for the protonpt distributions. We have gathered data from the other experiments at different energies. We find that the temperature increases with the rise in incident-particle energy, and it decreases as the multiplicity of the pions produced increases at a fixed incident energy.

Transverse momentum distribution of pions in two and six prong events from π−–p collisions at 7.0 GeV/c

We have measured the transverse momentum distribution (pt) of the pions produced in the BNL 80″ liquid hydrogen bubble chamber. The bubble chamber was exposed to a 7.0 GeV/c negative ipon beam. We have measured 1000 two prong and 2000 six prong events. The pt distribution for low multiplicity events represents production process via peripheral interactions whereas most of the high multiplicity events may correspond to collisions with large four momentum transfer to the nucleon. The p1 distribution of the pions has been fitted with an expression in the Hagedorn model forp,. The effective temperature obtained from a least square fit of the pion pt distribution for the two and six prong events is 132 ± 9 and 120 ± 3 MeV respectively. If we are justified in analyzing the pt distribution of the low multiplicity events with the Hagedorn model, we find that there is no significant difference in the temperature of the 'peripheral' and 'central' region of the interaction volume. The temperature increases with an increase in the energy of the interaction.