A burner comprising: - means for supplying the combustion air according to a predetermined flow rate; - means for supplying the fuel according to a predetermined flow rate; a combustion head comprising: an outer tubular body for channelling combustion air, said body extending along a main axis of the head to an emission portion thereof arranged in proximity to a flame; an inner tubular body for channelling a fuel, said body extending along said main axis of the head to an emission portion thereof arranged in proximity to the flame, said inner tubular body having a plurality of fuel emission conduits extending radially from the inner tubular body towards the outer tubular body; a diffuser extending between the inner tubular body and the outer tubular body, said diffuser being disc-shaped and having a diameter smaller than the diameter of the outer tubular body, there being defined a slot between said diffuser and the outer tubular body for passage of the combustion air at a peripheral area of the head,said fuel emission conduits having respective fuel outlet apertures arranged at the slot for passage of the combustion air so as to realize a mixture of the fuel and the combustion air; wherein the air supply means is connected between the inner tubular body and the outer tubular body and wherein the fuel supply means is connected to the inner tubular body; wherein the outer tubular body has a lip converging towards the main axis at the emission portion so as to define a narrowing of said slot for passage of the combustion air; characterized in that the dimensional ratio of the diameter of the diffuser to the diameter of the outer tubular body at the convergent lip is ranging between 0.78 and 0.9, so that for predefined flow rates of fuel and combustion air, the ratio of the velocity of the fuel exiting from the outlet aperture to the velocity of the combustion air exiting from the passage slot ranges between 1.8 and 3; and in that the means (101, 102) are configured to supply air and fuel at respectives flow rates in such a way that the ratio of the velocity of the fuel exiting from the outlet aperture to the velocity of the combustion air exiting from the passage slot ranges between 1.8 and 3. - means for supplying the combustion air according to a predetermined flow rate; - means for supplying the fuel according to a predetermined flow rate; an outer tubular body for channelling combustion air, said body extending along a main axis of the head to an emission portion thereof arranged in proximity to a flame; an inner tubular body for channelling a fuel, said body extending along said main axis of the head to an emission portion thereof arranged in proximity to the flame, said inner tubular body having a plurality of fuel emission conduits extending radially from the inner tubular body towards the outer tubular body; a diffuser extending between the inner tubular body and the outer tubular body, said diffuser being disc-shaped and having a diameter smaller than the diameter of the outer tubular body, there being defined a slot between said diffuser and the outer tubular body for passage of the combustion air at a peripheral area of the head,said fuel emission conduits having respective fuel outlet apertures arranged at the slot for passage of the combustion air so as to realize a mixture of the fuel and the combustion air; wherein the air supply means is connected between the inner tubular body and the outer tubular body and wherein the fuel supply means is connected to the inner tubular body; wherein the outer tubular body has a lip converging towards the main axis at the emission portion so as to define a narrowing of said slot for passage of the combustion air; characterized in that the dimensional ratio of the diameter of the diffuser to the diameter of the outer tubular body at the convergent lip is ranging between 0.78 and 0.9, so that for predefined flow rates of fuel and combustion air, the ratio of the velocity of the fuel exiting from the outlet aperture to the velocity of the combustion air exiting from the passage slot ranges between 1.8 and 3; and in that the means (101, 102) are configured to supply air and fuel at respectives flow rates in such a way that the ratio of the velocity of the fuel exiting from the outlet aperture to the velocity of the combustion air exiting from the passage slot ranges between 1.8 and 3.