Fix TRD pile-up information

Author: martenole

GPU/GPUTracking/DataTypes/GPUTRDInterfaceO2Track.h

@@ -77,10 +77,11 @@ class trackInterface<o2::track::TrackParCov> : public o2::track::TrackParCov
 
   GPUdi() void setPileUpDistance(unsigned char bwd, unsigned char fwd) { setUserField((((unsigned short)bwd) << 8) | fwd); }
   GPUdi() bool hasPileUpInfo() const { return getUserField() != 0; }
-  GPUdi() unsigned char getPileUpDistanceBwd() const { return ((unsigned char)getUserField()) >> 8; }
-  GPUdi() unsigned char getPileUpDistanceFwd() const { return ((unsigned char)getUserField()) & 255; }
+  GPUdi() bool hasPileUpInfoBothSides() const { return getPileUpDistanceBwd() > 0 && getPileUpDistanceFwd() > 0; }
+  GPUdi() unsigned char getPileUpDistanceBwd() const { return getUserField() >> 8; }
+  GPUdi() unsigned char getPileUpDistanceFwd() const { return getUserField() & 255; }
   GPUdi() unsigned short getPileUpSpan() const { return ((unsigned short)getPileUpDistanceBwd()) + getPileUpDistanceFwd(); }
-  GPUdi() float getPileUpMean() const { return 0.5 * ((float)getPileUpDistanceFwd()) - ((float)getPileUpDistanceBwd()); }
+  GPUdi() float getPileUpMean() const { return hasPileUpInfoBothSides() ? 0.5 * ((float)getPileUpDistanceFwd()) - ((float)getPileUpDistanceBwd()) : getPileUpDistanceFwd() + getPileUpDistanceBwd(); }
   GPUdi() float getPileUpTimeShiftMUS() const { return getPileUpMean() * o2::constants::lhc::LHCBunchSpacingMUS; }
   GPUdi() float getPileUpTimeErrorMUS() const { return getPileUpSpan() * o2::constants::lhc::LHCBunchSpacingMUS / 3.4641016; }